JEE 2024: Structure of Atom Class 11 | One Shot | 1 Month 11th Done | JEE Chemistry #jeepreparation

foreign [Music] today we are going to start as well as the end with the chapter structure of atom it is going to be about four to five hours but I promise that you will be able to understand each and every topic that can come in your board exam or in Jee Mains or in GE Advanced so watch the session very carefully so that you get at least 8 to 12 marks in J Mains or in advance because we can expect two to three questions from this chapter so let's get set go towards the board so the story of structure of atom starts right now now let's go and check it out how many topics are there and by the way I hope you can see this one month 11th will be done that means in this month July month we are going to complete the whole of class 11th and then we are going to start with 12th one shots as well but before that we are going to do topic wise lecture of class 12th anyway all of these later on let's check out how many topics are there now as you can see there are many many many topics yes let's let's go one by one so initially we will do discovery of subatomic particles now is this important in uh in in with respect to J Mains or Advanced not at all however these initial initial sum of the topics are very important to understand all of these hence we have to do it okay so like I said it is not important uh in J or uh J Mains or J Advanced however we have to study it so discovery of subatomic particles that means electrons protons and neutrons that these are the things that we're going to study then we start with the atomic models Thomson's atomic model Rutherford's atomic model and then there is a topic called distance of closest approach that is very important for J mains actually J Advanced however then developments leading to bores atomic model this is very important photoelectric effect dual behavior of electromagnetic radiation is important Atomic Spectra boards model for hydrogen atom towards quantum mechanical model of the atom all of these that you see orbitals and quantum number shapes of Atomic Mod orbitals energies of orbitals filling of orbitals in atom electromagnetic electronic configuration of atoms apart from these there are also certain topics that are inside these like Schrodinger's wave equation like uh uh Heisenberg's uncertainty principle of principal hoon's rule police exclusion all of these so in this session you will be once you are done with the chapter you will actually feel like I'm done with everything and now I'm not going to waste any more time let's start with discovery of electron so whatever structure that we know of right now was not how we thought to be right at certain point especially in the very beginning sir Dalton he thought that no atoms are the smallest particles and they are indivisible but later on he was proven to be wrong right with the first subatomic particles being discovered was this this was the experiment right now what exactly is this this is called as a cathode ray tube what is it called This is called as a cathode ray tube c r t you know the olden days in the olden days I mean when I was growing up we did not have this flat screen TV or you know OLED the curved TV or LED TV we did not have all of these we had those bulky kind of TV where you had to go there and change the knobs and everything right in those days we used to call the TV to be CRT TV it's called as basically nothing but this cathode ray tube right cathode array two that's exactly what it was now actually it looked like this actually it looked like this however we will not be able to understand things from here which is why this makes it more easier for us to understand so in this cathode ray tube if you look very carefully it might look very complicated actually there is nothing much there is a cathode here yes there is a cathode here as you can see do you see this this is the cathode that's a negatively charged electrode and here is your anode right anode is the positively charged particle ah sorry positively charged electrode and here there is a vacuum pump here there is a vacuum pump with this what they did was they removed most of the air particles now if you remove the air particles do you understand that air is at a very low pressure right so can I just write it down that air here is at low pressure air is at low pressure all right and why low pressure if the question comes in your mind that why have we taken air to be at low pressure that's because you know that air is a bad conductor of electricity isn't it so if you take many many air particles it will be tougher for you to make them conducting correct so that is why we take Air at low pressure that is maximum amount of the air particles we have removed and we have used a high voltage generator here okay so high voltage low pressure and when the electricity flows inside this tube what happens is we start seeing that electrons have come out but do we actually see it no electrons are not visible yeah you cannot see them really but you can see the behavior of them you can see the effect that they are producing and what is that effect furthermore what we did was we we used a fluorescent screen here when we used a fluorescent screen here these electrons they were or these cathode rays the Rays that are coming out of the cathode they hit they strike this surface and you could see something you could see a spark you could see something coming out of it at this spot you could see that there was a light there was a spark something coming out of it which means that there was definitely something that was coming out of the cathode that proved our Point even more so let's just check out what exactly how we learned here in this case we have learned that the cathode rays they start from the cathode and they move towards the anode correct this is exactly what we read the cathode they start from the cathode they move towards the anode right like this they come okay all right these Rays they are not visible that's exactly what I said they are not at all visible but you can see the behavior you can see the effect that they are producing okay yeah cool cool with this much right now read the third point in the absence of electrical or magnetic field they travel in straight line but if there is an electric field or a magnetic field what happens that we will study in the next slide but before that yes you have understood that without any electrical field or magnetic field C how they are traveling here straight lines straight lines straight lines got it yeah now in the presence of magnetic field and electric field what happens is they start behaving like a negatively charged particle and that told us that yo these Rays they have certain particles which are basically negative and we know today that electrons are negatively charged particle right so proven everything is proven hence proof does proof we got it right fifth point is the characteristic of this cathode rays they do not depend upon the materials of the electrodes whatever you take here cathode and cathode and anode whatever you take here it doesn't matter on them right it doesn't depend on what gas do you have here what gas you have here doesn't matter any gas that you take all the particles they behave like this okay all right so that means that electrons do not depend on the material of the electrodes it doesn't depend on the gas that you have taken inside got it yeah great now moving on from here so I told you right how do they behave in case of an electric and a magnetic field now if you take an electric field so this this part that you see this is electric field yes these are the electric field yes and this north south that you see this is the magnetic fit now do you see that this is the rain right this is the ray here so if you see if you look carefully and imagine that this is a 3D picture so basically what is happening is these the electric field the magnetic field and the Rays they are all perpendicular to each other which means let's take a look at it so if this is my remote this is my Ray this is my cathode ray this is my electric field the pen is the electric field and this is my magnetic field this is my magnetic field understanding all of them are 90 degree 90 degree 90 degree perpendicular exactly so that's what we did right now when we have taken it like this when we applied electrical field the Rays that traveled like this and they hit the spot a when we have taken the magnetic field we saw that the Rays they bent and they hit the position C but without any of this field we saw that they are hitting the point B that means without any field they are traveling straight line remember they are traveling in a straight line with electric field they are bending and they are hitting the a position with magnetic field they are bending and they are hitting the seat position okay so this is what we see so what we have seen something great but from from here what do we understand well let's understand that from here we understand the deviation of particles from the path in the presence of electric or magnetic field it depends upon three things what are these three things number one is the magnitude of the negative charge what is magnitude magnitude is basically the number the strength of the negative charge what is magnitude once again magnitude means the strength okay the strength of the negative charge then number two factor is the mass of the particle yes what is the mass of the particle higher is the mass greater is the deflection if the mass is higher then the deflection becomes higher and it also depends on the strength of the electrical or magnetic field so when you change the magnitude of the electric or the magnetic field you saw that there was a change there was a change okay all right now from here from here in your ncrt you will also find that charge to mass ratio what is charge to mass ratio e by m e if I take it was found out to be it was found out to be let's check it out guys okay let's check it out even five eight eight two zero eight eight two zero that's it is that all no into 10 to the power 11 okay into 10 to the power 11 coulomb per kg all right correct so this is your electron this is your charge by mass ratio all right got it now since electrons are negatively charged what happens the charge on the electron is considered to be minus E okay we know that electrons are negatively charged so we take the charge to be minus E got it here yes so the E by m a ratio was found to be this it was found to be this clear clear clear clear clear clear everyone great okay so what did I say once again m e is the mass of electron you know what let's write it down here m e is basically the mass of electron all right yes I hope my handwriting is visible right mass of electron in mass of electron and E is what what is e what is he I just told him I just told you guys and E is the magnitude of the charge okay e is the magnitude of the charge okay this is in coulomb and this is in kg all right yes cut it clear now what happened there was this another person called milk right what did Milliken do Millikan only did this experiment called oil drop method what happened in this oil drop method basically he took a he took something like this okay he took a tube like this and here there was an oil atomizer what is this oil atomizer have you seen in the olden days in rickshaws you had those uh you know you could you could just press like this and you choose to make a sound like like like a horn exactly so this is that oil oil atomizer and here in this part you have actually kept some oil so when you press this what happens is droplets of oil go into this chamber okay droplets of the oil go into this chamber yes very small tiny droplets right now when they reach this top plate this is where you have this is these are basically the electrodes that you have okay you have connected you have connected yes you have connected some Source here so electricity is flowing through here now when they reach this top part the top plate after passing through the top plate and at this point of time some X-rays were also sent into the chamber okay yes X-rays were also sent into the chamber and now the soil droplets they are passing through here the oil droplets have come here right the oil droplets have come here and the x-rays are also made to pass through this chamber now what happens is when the oil droplets they collided when the oil droplets we collided with the charges they started to behave like a Charged particle now in this case the particles movement were dictated by gravitational force obviously because it is coming down as you can see gravitational force now it also started it also started to act like a Charged particle now correct yes everybody so it if it started to behave like a Charged particle so that means there are some other other forces also of course electrical field now yes electrical field or electrical force apart from that because they are moving so there is also drag force that is acting on them okay so these three forces are acting on them and they are coming down now you can see through this microscope or through this eyepiece here right you can see through this eyepiece and what happened was when you increase the when you increase the current flowing through it or you decreased it the particles were either or they accelerated like either they were either they were stopping they were refraining from movement or they started to move very fast okay let's take a look at it so this is exactly what happens see the oils the oil droplets are falling here x-ray is passing through the moment they hit it you can see through here see and they started behaving like a Charged particle and they started behaving like a Charged particle so when you increase the when you increase the currency CC you increase the current the speed increased see this this Arrow you increase the current the speed increase as you decrease it the speed of the particles moving in the chamber decreased I hope this is clear yes so Millie can concluded that the magnitude of electric charge Q on the droplets it's always an integral multiple of the electric charge so in integral multiple of the electric charge e that is Q is equal to n multiplied with e let me write that down okay let me uh write that down yeah I'm gonna write it here I'm going to write it here so take a look at it I said that Milliken concluded that concluded that the magnitude that the magnitude of electric charge of electrical charge Q on the droplets okay on the droplets on the droplets is always is always an integral multiple integral multiple of the I hope you this is visible is it going to down anyway I'll be giving you the PDF so don't worry about it okay I'll be giving you the PDF an integral multiple of the electrical charge okay all right that means that that means this means that Q is equal to n multiplied with e this is our formula this is our formula got it clear okay all right so all of these are clear so sorry I was about to fall anyway moving on now let's understand charge on electron what is the charge on electron yes what is the charge on electron let's check it out what is the charge on electron I'm pretty sure that you all can tell me yes it is minus 1.6 into this yes all right yes and the present value this this is what we came out with yes and the present value today is 1.60 2 1 7 6 okay 1.602176 into 10 to the power what same thing yeah okay this is the present value now if you have to find the mass of the electron remember what we did was e by m e and all of that right we did this e by m e now if we have to find out the mass of electron that Thompson had given that was given by Thomson right so mass of electron if we have to find out what will we do what will we do let's take that m e is equal to okay m e is equal to let's do e by E by m e so this value we already know this value we know from here so if we put it 1.60 2 1 7 6 into 10 to the power minus 19c divide it by divided by what what was the value here the value was 1.758820 into 10 to the power 11 right so 1.758820 into 10 to the power 11 coulomb per kg right so when you solve this when you solve this you find a value which is 9.1094 into 10 to the power minus 31 what is the mass the mass is 9.1094 [Music] into the 10 to the power minus 31 that is the answer coulomb coulomb cancel so this will be kg this is the answer okay this is the value of mass of electron got it so till now we are done with electrons completely now when we go forward we have to understand discovery of proton so basically you take the same thing you say take the same discharge tube okay take the same discharge tube you have a fluorescent screen coating here right and here one thing that you have done is you have taken a perforated anode what have you taken perforated what do you mean by perforated by perforated we don't mean anything but it's just a fancy name for holes basically in the anode there are two small holes in it okay so you have taken a perforated anode and the same way you have high voltage but you have low pressure right low pressure here low pressure you have and you have high voltage correct so low pressure high voltage the current passes through and from at from cathode obviously as usual there are there are cathode rays that are coming out but now what happens is now what happens is we saw here that although the electrons were coming out but after some time after they have went through this perforated anode and they met the fluorescent coating then they started to come out from this side somehow we saw that from the anode like they they went from here like this they went from here like this right but after hitting them then what happened was the direction somehow changed okay what happened the directions somehow changed now and because the Direction Changed we started to call them Canal race what did we start to call them we started to call them Canal Rays or the anode Rays so if you are thinking that we started to call them anode Rays because they were coming from anode actually no they don't come out from anode they come from here they come from the cathode but after hitting the fluorescent coating then they go back and that's why we started to call them anode Trace okay so what are the things that we saw here we saw that the mass of the positively charged particles this time it depended upon the nature of the gas in the last one in the discovery of electron we saw that it did not depend on the gas but here it did depend on the nature of the gas all right yes moving on from here now what happens see the charge to mass ratio of the particle also dependent on the gas from where they originate the charge by mass ratio also dependent on the gas you're getting my point then some of the positively charged particles they carry a multiple of the fundamental unit of electrical charge the positively charged particles they carry a multiple of the fundamental unit of electrical charge so whatever is the electrical charge you basically now put a n you put a multiple of it and that's the result that you get and this time we also saw that the behavior of this particles in the magnetic or the electric field was opposite to what we saw in the in the discovery of electron so that means these are opposite to the charge that electrons were carrying so electrons were carrying negatively charged As We Know protons are carrying positive charge now let's go and take a look at the discovery of nutrients also so who discovered neutrons if you want to know it was discovered by Chadwick it was discovered by Chadwick okay yes Chadwick discovered in 1932. so in 1932 what he did was alpha particles that were coming out from polonium do you know what is alpha particles if you do not know alpha particles are basically those that have two positive charge have two positive charge okay alpha particles have two positive charge all right yeah okay two positive charge and mass four two positive charge Mass 4. Mass has to be 4 right so the alpha particles that were coming from polonium okay the alpha particles that were coming from alpha particle source is what source is polonium you can write it down although this will not come in the exam but this is just good to know general knowledge okay so the alpha particles that were coming out from polonium were made to be bombarded on beryllium they were made they were made to you know hit the beryllium all right and when they hit the beryllium okay what did we see we saw neutrons coming out okay we saw neutrons coming out so basically if I write it like this foreign any idea why did I write 0 here because neutrons as the name suggests they are neutral in nature yes they are neutral in nature no charges they have no charges cool but they have mass they have mass but they have no charges hence this is how we have written them all right so with this node all the subatomic particles we are done with all the discoveries of subatomic particles are there the properties of fundamental resource this is something that you should know I have just you know copied and pasted it from ncrt this is there in your ncrt as you will see you will see that the symbols are EPN that is electron proton neutron absolute charges are there relative charges are there this is what we take and and mostly this is what we will take to calculate right now mass per kg is also given to you mass per U is also given to you approximate Mass but you is also given to you shall we solve a question let's solve a question so the question is the ratio of charge to mass of an electron in coulomb this is not coulombs this is coulomb coulomb per gram was determined by JJ Thomson right yes that e by m e value thing now he determine this ratio by measuring the deflection of cathode rays in electric and magnetic wave what value did you find for this ratio what value did you find the answer is obviously 1.7588 so 7588 we can we can definitely keep it as 1.76 into 10 to the power 8 coulomb power gram this is per gram but what we learned was per kg so from per kg if you convert it to gram it will be instead of 10 to the power 11 you can write it as 10 to the power 8 done great amazing so done and dusted you guys are getting good at it moving on to the next question how many number of electrons are present in a particle which carries a charge of 5.5 into 10 to the power minus 16 coulomb this is very easy guys what you have to the formula that you have to use is n is equal to n is equal to see Q is equal to n e right yes what we learned was wait a second let me write it down properly yeah so what we learned is Q is equal to n multiplied with e so that means n is equal to Q by E agreed agreed everybody great now what we know is C what is given to us what is given to us in a particle which carries a charge of 5.5 into 10 to the power minus 16. so 5.5 into 10 to the power what is going on right this is what I write and what is my e value everybody knows 1.6 into 10 to the power minus 19 right so 1.6 into 10 to the power minus 90. correct now when you calculate this what is the answer that you you will get you find that out find that out find that out okay this is just simple calculation I think you'll be able to do it but anyways the answer is option A all right the answer is option a moving on the increasing order for the values of charge by mass is understand the question they are asking you they are asking you basically to find the charge by mass ratio of neutron charged by mass ratio of alpha particle charge by mass ratio of proton charge by mass ratio of electron this is what you have to find out all right now once you have found that out then see which one is the greatest let's do it now see the charge by mass ratio the charge by mass ratio of neutron is equal to what it'll be zero no charge is zero so anything that is 0 divided by 1 is equal to 0 so n is 0. now let's find it for uh let's find it for proton let's say yeah Neutron then proton for proton what will it be one what will it be charge is one mass is also one so one yes for electron let's do it charge is 1 divided by what is mass what is mass mass will be around 1 by 1 8 3 7. so this is very very very small and for Alpha if I find out for what is alpha alpha is two by four Alpha is two by four so first is this this is our number one yes then comes this this then comes this yes and then finally is this this has the lowest value this has the lowest value so uh I think it's option D I think it's option D yeah option D is the correct answer got it cool now now now now now now now let's study about atomic number and mass number so you all understood that discovery of the discovery of subatomic particles where we found out that there are electrons there are protons and there are neutrons electrons are negatively charged protons are positively charged neutrons are neutral okay please listen to the basics carefully I know you might think that man this is very easy why are you taking why are you taking so much time bitter please just give it a little bit time revise it properly only then we will be able to fast and Fast complete the chapter okay so atomic number let's what is atomic number everybody knows it come on don't tell me that you do not know let me change the color of the pen though let's make it yellow yes so the number of protons present in the nucleus is equal to atomic number what did I say the number of protons present in the nucleus is equal to atomic number so how do we denote atomic number atomic number is denoted with the letter Z okay how is it denoted it's denoted with the letter Z so let's write it down here what is atomic number atomic number is number of protons number of protons in the nucleus of an atom all right this is also equal to because because atom is a neutral right for the neutrality of the atom sometimes we can also write it as a number of electrons foreign now next thing is mass number what is mass number protons and neutrons present in the nucleus are collectively known as nucleus yes protons and neutrons that are present in the nucleus are collectively known as nuclides actually yes but anyway yeah so the total number of nucleons all right oh did I say nuclides no nucleons sorry my bad my bad yeah so the total number of nucleons is termed as mass number let's write it down is termed as mass number what are nucleons all right this is it so basically if I have to write down the formula now like this what is mass number mass number is denoted with capital a all right how do we denote it capital A that is basically number of protons Plus number of neutrons cool yes this we have understood now this number of protons can also be basically your Z and this is your n all right so atomic number plus number of neutrons is going to give you mass number don't be confused mass number is denoted with capital A and atomic number is capital is denoted with capital Z okay yes so if you are thinking that Mom these are very easy and I don't want to learn guess what this is the session this is the only session that you need to watch for your boards for your msat for your iitjee Mains for your J Advance anything and everything will be covered here so please sit back and relax take some Popcorn get a notebook and a pen and write it down while I am teaching you so that you don't have to watch it later and make the notes all right now we have understood the composition of atom right composition of atom is understood by us that atom has electrons neutrons and protons and we have understood that uh you know what is atomic mass number what is what is atomic number what is mass number so the composition of an atom an atom can also be written as basically X this is the symbol here you write down the mass number and here you write down the atomic number okay all right everybody let me write that down again very clearly what did I say I said that this is the symbol this is the symbol of the element here is the atomic mass number and here is the atomic number so what did I say x is the symbol of element a mass number as you know and z atomic number this is how we basically denote an element okay this is how we denote an element but coming to the fact that there are several other terms that we are going to use in this chapter so let's learn that all one by one first one is isotopes what what are isotopes I think everybody all of you know it right what are isotopes which are what are isotopes Isotopes are basically atoms with identical atomic number but different mass number yes what are isotopes atoms with identical atomic number but different mass number correct yes we have understood this amazing now what are ISO bars let's understand that also what are isobars isobars are the atoms with same mass number but different atomic number thank you yes what is the example that I can give example would be 14 C 6 and 14 7n note down guys yes this is a possibility okay this is a possibility actually no it cannot be 12 it cannot be 14 I think it should be 12 only no six seven no no clear this is five this is fine yeah no mistakes I think I'm sorted cool okay now moving on are these the only two things that we need to know no if we are going to go for James and there are several other terms also that we need to know third term let's take isotones what are isotones isotones are basically the elements having the same number of neutrons that is when you do mass number minus atomic number the number that you will get yes isotones elements having same number of neutrons let's write it down okay this is your isotones now comes ISO ISO steps okay now comes another term called ISO stores what is this now this you might be hearing for the first time okay isostos are species that have the same number of atoms and electrons okay species that have same number of atoms and electrons foreign yes next comes I saw die first yes ISO die F first let's write that down what are isodipers ISO diphers are basically the elements that have the same number of let's check it out okay a minus 2 Z okay now why am I writing this symbol not a bracket that means that we are also always going to take the positive value okay we are also always going to take the positive value now comes another town called isoelectronic species what are isoelectronic species isoelectronic species what do they have they have the tell me tell me tell me tell me tell me species having the species or the elements which have the same number of electron okay so species or elements having the same number of electrons all right great there are some more terms there's something called as paramagnetic and diamagnetic just know it yes just know it although we will not need it in this chapter but just know it because paramagnetic and diamagnetic also supposedly come because of the unpaired electrons right the species those who have non-zero unpaired electron or the species that have unpaired electrons okay or elements species or elements right let's write both species or or atoms actually not elements species or atoms having at least one unpaired electron okay this is your paramagnetic and finally the last one is of course di a magnetic what is diamagnetic species or atoms which do not have which have zero unpaired electron basically so let's write it down so species atoms have zero unpaired electron that means they do not have any unpaired electrons okay they do not have any unpaired electrons all the electrons that they have are actually paired with each other so these are all the terms that you should know you don't have to like really really remember the definition but just know that what are these because these will uh you know these are the terms that will be used in your exam and you will have to know the answer correct so with this note now let's go to the Thompson's atomic model that means we are starting with the new section of the chapter that is uh atomic model so Thompson's atomic model I think everybody knows this is also called as the plum pudding model or the watermelon model yes what is this called as the plum pudding model now obviously we are Indian so we do not know what exactly is plum pudding because let's just let's just face the truth truth bomb here we don't eat Plum Pudding who is plum pudding yeah I mean plum cake sure during Christmas only that too so anyway uh Thompson was a what English man right he was an English man and obviously he was born and brought up by eating Plum Pudding right he was eating a lot of Plum Pudding especially during the Christmas and that's when an idea struck in his mind and he was like you know what the atom probably looks like the plum pudding right he said that that the whole thing is of a positive sphere this whole thing is positive sphere and in between there are electrons engraved in it what do we mean by engraved have you seen how watermelon seeds are just engraved in it like you actually have to scooping a scoop it out with your nail or a spoon or something like that exactly so that that that how the seeds are present in the watermelon that exactly is called as engraved okay yeah look it up look look it up in the dictionary anyway so basically he said that the whole red part if you imagine a watermelon or you have seen it so imagine if this is a watermelon the whole red part is basically the positive sphere and he said that this this the seeds they are the electrons now obviously this was a great model I know it doesn't sound very great it sounds very stupid however this did prove that this did explain the neutrality of the atom but apart from that when Rutherford came into picture and when he did this experiment the famous experiment drew the first gold foil experiment which you have also learned about it in your Junior classes but just a recap quickly so this was a source this is called as a collimator yes what is it called it is called as a collimator so from The Source alpha particles were bombarded into gold foil why was gold foil taken you know that it is malleable it is highly malleable so you could be beat it up beat it up beat it up just beat it right when you just beat it it keeps getting thinner and thinner so you could take a very thin sheet where they were very uh you know there were thousand atoms that that was the thickness of the sheet right so when he took this right and then the results that he saw right the results that he saw and there was also a zinc sulfide you know there was also a zinc sulfide um what do you call collar kind of thing yes collar kind of thing and then the results that were seen was Rutherford and his students actually Rutherford was the teacher there were two students their name was Hans Geiger and uh on Ernest Marsden yeah now Geiger's name you have heard uh in physics you will be studying about something called as Giger Muller counter yeah you will be learning about it so that Giga is the same gigger yes anyway so Hans Geiger and Ernst Marsden they actually did the experiment because obviously he was the teacher he took all the credit away right so they did this experiment where a stream of high energy alpha particles from a radioactive Source was directed in thin foil yes the thin foil was 100 nanometer right now the thin gold foil it had a fluorescent zinc sulfide screen around it I said caller it's it's a screen basically and whenever the alpha particles they they struck the screen a tiny flashlight was produced at a point now check out what actually happened right so basically the alpha part because they were coming the alpha particles were coming see how some of them deflected some of them deflected with a smaller angle and some of them they they came near the nucleus and they went they went exactly in the same straight line as they had come here so basically what he observed was you observed that most of the alpha particles they just passed straight without anything they just came and they just went ahead nothing happened they just went ahead okay then there were some where there was a small deflection they they went away they bent away from they bent away from the straight line with a very small angle then there were some who took a large deflection yes and there were some which just turned back as it is so basically the conclusion was that that most of the space in the inside of an atom is actually empty right yes and alpha particles because they were positively charged from the he they were positively charged helium nuclei right they can be deviated from a positive charge correct we know it very from a very basic point of view we know that like charges repel like charges unlike charges stating they attract each other right that's exactly what happened here yes so there definitely must be some positively charged region inside the atom which repelled the alpha particle that was the conclusion very smart right now only few are particles they deviated they deviated yes and that means that the positively charged in region the positively charged region inside the atom was actually very less so I can also write it that if if let's say that radius of nuclei is actually much much lesser than the radius of the atom this I can write it right yes so the positively charge of the atom the positive charge of the atom is concentrated in a minuscule region minus Q means it's very small region yes that is called as a nucleus so the radius of the nucleus is 10 to the power minus 15 meter and that of an atom is 10 to the power 10 so if the atom is in angstrom then the radius of the nuclei is in Fermi you get my point you get done you you get the difference yeah so it's like this okay now what happened was of course it was a greater stepping Soul a stone right it was a great milestone in in the whole chemistry's history however there were limitations there definitely were limitation but let's just let's go into that a little later let's understand that an atom consists of the tiny positively charged nucleus at its Center the nucleus contain positively charged particles almost entire mass of the atom is actually focused on the nucleus and all the positive charge is concentrated in the nucleus yeah okay everybody getting my point yes nucleus all right okay yes electrons that revolve around the nucleus in circular paths called as orbits yes and this model resembles the solar system right in circular Parts basically they revolve around concentric circles right so basically if this is your nucleus then this is this is these are the path of your electrons right the electron and the nucleus they are held together because of electrostatic charges there is positive charge there is negative charge so what will happen electrostatic force of attraction positive and negative unlike charges they were getting attracted electrostatic force of attraction was there which is why the atoms was not falling apart it was right there it was properly held together but there was of course limitation what happened in the limitation so you understand that it does not obey the Maxwell's theory of electrodynamics you were probably asking ma'am what is this Maxwell's theory of electrodynamics nothing very easy so what Maxwell said that so if an electron is moving around the nucleus right if something is moving around like this in a in a in a in a circular orbit that means that when the electron is moving it is emitting energy because it's an accelerated motion it is it is it is getting accelerated and it's moving it's continuously changing the direction right in a circular orbit you are always changing the direction so when you are always changing the direction is an accelerated motion if it is an accelerated motion that means that the electron is supposed to emit energy and constantly if it is emitting energy that means there may be a time when it does not have energy and it will fall into the nucleus and everything and anything is gone the atom will not be stable like how we see it that's what Maxwell said so according to this Theory a small charged particle if it is moving around an oppositely charged Center it is continuously losing energy and if an electron does so that means that there has to be a time when it is like it falls but it's not happening if that happens then we have to question the whole existence of matter you get my point so if electrons are constantly radiating energy then it is a Spectra then its Spectra has to be continuous but that's again not the case later on we found out that no Spectra is not continuous it was actually lime atoms were giving lines better we will learn about it we will learn about it okay so there was a limitation but now there is a topic called as distance of closest approach this is very important from Jee Mains and advanced point of view very important please do read it okay please do read it so basically you have to understand that distance of closest approach the literal meaning of this sentence says that the literary meaning of the sentence is basically what it's saying is alpha particle is coming coming coming coming coming right it is traveling traveling traveling traveling traveling and then it sees something and it turns back right what happens when you are bunking a Class A bunking a class in your school yeah let's just say that you went to the canteen you went to the playground and everything you wanted to go to the canteen and the uh playground obviously to play something or just just pass the time right so you went you came out of the washroom and you're going like you know with full-fledged like salmon boy like salmon boy you're going like this and then what happened you see principal so you were like um oh you went this is what you did correct exactly exactly exactly now check out what is happening here yep check out what is happening so imagine that imagine that this is my alpha particle this is my alpha particle right and this is my gold foil this is my gold foil Au gold this also has positively charged nucleus right this has a positively charged nucleus so what is actually happening is this is coming coming coming coming yes it still keeps coming and then what happens at certain point it's like no I'm not gonna go beyond this point it says that I am not going to go beyond this point yep yes and then what it does is it just turns back just turns back and comes this side so initially it started to come out like this it went went went at this point at this point it came back it's like nah I'm not going Beyond this I'm not going Beyond this now when the alpha particle started moving would you understand that there is kinetic energy because it started to move also it will have potential energy correct it will have kinetic energy and potential energy and even at this point it will have kinetic energy plus potential energy right right everybody clear Ed so what is the kinetic energy here kinetic energy is definitely half MV Square correct what is the potential energy is k Q 1 Q 2 by r correct yes okay this q1 and Q2 this Q one and Q2 let's let it be like this only or I can also write this Q 1 Q 2 as just just take a look at it I can also write it as k 2E yes k 2 e into z e divided by R okay I can also write it as 2 e z e divided by R which will make it to be K to z e Square by R clear all right now where do I get the r from I can call this distance to be R okay I can call this distance to be R all right yes so here it is coming out with some velocity the alpha particle is coming out with some velocity this is my R distance and from here to here if I take my R is let's say R Dash this is a very large r this is very large okay so here I can write half MV Square this is my kinetic energy Now what is my p e my PE here will be my dear students please take a look at it I just wrote that P is k z e Square k 2 e wait a second yes this is my P my P is k 2 z e Square divided by R but I just told you that R is very large Infinity if that is the case then I can write it to be 0 yes why did I do that because R is very large so I'm writing it as 0 this will be equal to now see the alpha particle is going going going it came till here and then what happened what do you do when you are going going you saw the principle you stood like this for some time and then you turned back right it wasn't like this and it doesn't happen like this right it does not happen like this you stood there you saw the principle and then you turned back so at certain point your velocity was Zero right your velocity was Zero yes so that means at this point I can write my kinetic energy to be 0 and my potential energy will be k z e Square divided by R and here 2. yes so that means that I can write it to be half MV square is equal to 2 k z e Square divided by r got it yes or I can also write it to be R is equal to what will be my R my R will be see this 2 will go here so 4 k z e Square divided by m v Square got it yeah is this clear everybody is this clear is there anything that gets canceled somewhere anything that gets canceled somewhere this is what it is correct so now write down what is what now write down what is what okay what is my M what is my m m is the mass of particle okay let's write it down here n is mass of particle yes okay all right what is k k is equal to 9 into 10 to the power 9 correct yes what is z z is the atomic number Z is the atomic number all right yes then what is e e also you know e is 1.6 into 10 to the power minus 19c yes then what is v v is velocity V is velocity all right so this is what is distance of closest approach please do remember it it is very important for J Mains and J Advanced cool all right everybody understood distance of closest approach now moving on from here okay moving on from here I think I did everything here only I was supposed to do bits of it here so when the alpha particle approaches the nucleus to make a head-on collision with the nucleus the alpha particle approaches the nucleus yes it approaches a nucleus until until what until R is equal to 4 k z e Square divided by m v Square this is your formula okay this is your formula understood everybody got it clear now let's do a question here all right let's do a question here come on read the question everybody read the question the question is how many neutrons are there in 88 strontium 38 this is very easy all you have to do is 88 minus 38 is equal to 88 minus 38 is equal to what 50 so the correct answer is of course option b got it all right yes amazing moving on to the next question which of the following conclusions could not be derived from Rutherford's alpha particles scattering experiment most of the space in the atom is empty this was true radius of the atom is about 10 to the power minus 10 in y m 10 to the power minus 10 meter while that of nucleus this is also true electrons move in a circular path of fixed energy called orbits electrons and the nucleus are held together this is the correct answer he never said anything about orbits he never said anything about orbits did he he didn't yeah fixed energy fixed energy called orbits that he did not say orbits yes he said that concentric circles like the uh Solar Planet system and everything but he did not say anything about fixed energy called orbits right so option C is the correct answer great next question guys which of the following pair is ISO diaphores what was the formula the formula was a minus 2 Z correct not bracket it has to be straight line foreign so let's do it for each one of them then what is the what is the mass number the mass number for the first option you see 14 minus 2 into 6 so 2 6 the 12 14 minus 12 is equal to 2 correct now if I take it for sodium 23 minus 2 into 11 is equal to 23 minus 22 is equal to 1 so this is definitely not the answer next one if you do 24 minus 2 into 12 is 24 minus 24 so 0 but 23 minus this is 1 so this is also not the answer option C let's check it out 4 minus 2 into 2 is equal to 0 and then 16 minus 2 into 8 is equal to 0 2 so option C is the correct answer gamma Point yes clear amazing another question another question see you will be able to do it so this is related to the distance of closer approach let's say check it out so beam of specific kind of particles of velocity 2.1 into 10 to the power 7 meter per second is catered by a gold catered by a gold nuclei Z is equal to 79. find out specific charge by mass of this particle if the distance of the closest approach is this so R is given to us my dear student R is equal to 2.5 into 10 to the power minus 14 meter right yes we have this correct V is also given to us the V is 2.1 into 10 to the power 7 meter per second Z is given to us that is 79 right yes we have to find charge by mass ratio so at the closest point when the alpha particle is closest to the nucleus right what happens initial energy is equal to kinetic energy right what do we know we saw that the initial kinetic energy right initial kinetic energy is equal to the potential energy so that means that half MV square is equal to 2 k z e Square divided by R is that correct yes that's what we know that's what we no am I right but instead of now instead of writing 2 k z e Square divided by r can I write it to be can I write it to be k q 1 and Q2 can I write it to be q1 and Q 2 by r I can right I can this can be equal to do I have to write 2 now do I have to write 2 no I don't have to write 2 okay I don't have to write 2 so what I'll do is see I will do K Q 1 Q 2 pi r all right yes this is the thing now what I will do is now what I will do is check it out q1 I know Q2 by m if I do okay Q 2 by m will be equal to r v Square yes divided by divided by oh I'm so sorry here will be a z also here will be a z also okay yes what will it be it will be divided by 2 k q 1 Z am I making a mistake somewhere 2K Ze Square oh Q 2 also has to be there you know what let's do it again okay here is a question for you next question a beam of specific kind of particles of velocity 2.1 into 10 to the power 7 meter per second is catered by a gold nuclei Z is equal to 79. you have to find out the specific charge that is charged by mass of this particle if the distance of closest approach is 2.5 into 10 to the power minus 40 meter all right okay so what are the thing that we know distance of closest approach that means R is equal to 2 point 5 into 10 to the power minus 14 meter velocity is given to us velocity is 2.1 into 10 to the power 7 yes atomic number is given to us so Z is equal to 79 it's given to us we have to find out the specific charge that is charge by mass ratio okay now we know that at the closest distance we just saw no initial kinetic energy correct initial kinetic energy is equal to p correct yes so that means that half MV square is equal to 2 k z q 1 Q 2 by r if you remember right yes now what I can do is I can write it like this also Q2 by m is equal to r Q 2 by m is equal to RV Square divided by 2 k z q 1 can I write it like this I can now check it out what I'm gonna do what is my R my R is 2.5 into 10 to the power minus 14 M all right what is my V my V is 2.1 into 10 to the power 7 Square divided by 2 into Z is 79 q k is 9 into 10 to the power 9 and uh q1 I can write it to be 1.6 into 10 to the power minus 90. correct solve this once you solve this once you solve all of this I think your answer has to be around Square 7 to 14 14 will get canceled right here then 19 and 9 10 will be remaining 2 into 79 and then 2.5 it has to be around option A option A will be the correct answer if you solve it great option A will be the correct answer great now my dear students we are moving towards the best part of the chapter that is developments that led to the board's atomic model what really happened that made Bohr reach towards his atomic model so you know there were lot of data there were lot of observed studies that he kept saying about the interactions of radiations with matter and all of that he saw right now there were two developments that actually played the role that actually played the greatest role in the formulation of atomic model that Bohr made it right one was dual character of the electromagnetic radiation which meant that the radiation can be like a wave or it can be like a particle okay and there were some experimental results regarding the atomic Spectra which made him come to the electromagnetic radiation now what is electromagnetic radiation let's understand what is electromagnetic radiation when electrically charged particle moves under acceleration write it down when I'm so sorry my handwriting sucks big time I'm trying to make it better but anyway let's write it again okay when electrically charged particle I said okay when electrically charged particle electrically charged particle moves under acceleration this is moves under acceleration what happens alternating electrical and magnetic field are produced okay alternating electrical and magnetic field are produced and transmitted okay yes so these fields are transmitted in the form of waves these fields however they transmitted these fields are transmitted in the form of waves okay these fields are what did I say transmitted in the form of waves in the form of wave called you got it right electromagnetic waves or radiation yes called electromagnetic waves okay so basically if I have a let's say a particle if I have a particle right if I have a electrically charged particle and then if I accelerate it what will happen there will be some waves that will come out and these are called as your EM waves or electromagnetic radiation clear now how does it look like how does it look like it actually is now if you see carefully look at it so if this is your electric field this is your magnetic field both are perpendicular to each other yes both are perpendicular to each other like this and there is the wave that is traveling in a Direction so all the three of them are actually once again remember all of them how they were perpendicular so like this like this and like this correct yes this is how they are all perpendicular okay so like this they are all perpendicular to each other and see if this is your if this is your electric field then this is your magnetic field okay and these two together this whole eight thing that you see this is together your length of the electromagnetic waves okay now let's understand that what actually we saw the oscillating electric and magnetic field produced by oscillating charged particles they are perpendicular to each other which is what I just told you right this is what we just told now unlike the sound way sound waves they always yes or waves produced in water you know that sound waves are like a child they always need a medium but hey they don't need a medium they can also travel in vacuum okay yes number three are that there are many type of electromagnetic radiations and they are different from each other how in wavelength or frequency now what are this we are going to learn in some time now these constitute what is called as electromagnetic Spectra now because there are different wavelength and different frequency which is why you are getting different sort of electromagnetic radiations together when you look at all of them you are going to get something called as electromagnetic spectrum what is Spectrum spectrum is basically from this it started from that it in from from here here it ended so basically if you take a prism if you take a prism shine light like this it will the light will you know scatter into many different colors that is called as whip gear violet indigo blue green yellow orange so that that visible range that you see the visible range of colors that you see violet indigo blue green yellow orange red that is your nothing but Spectrum that's the visible range Spectrum it starts from Violet and generate okay that's the Spectrum so same thing like that you also have an electromagnetic spectrum we're going to read about it right and different kinds of units are used to represent electromagnetic radiation so fourth point is back now let's talk about the properties or the characteristic of electromagnetic wave or electromagnetic radiation obviously whenever we talk about something we need to know about the properties you know how when a new teacher comes you always ask ma'am which IIT do you belong to Sir how much was your marks sir how many people have you talked these are what a teacher's properties right the same like that you are going to ask about the properties of electromagnetic radiation also now I know you have to study more but learning so the first one is let's talk about frequency what is frequency my dear student okay let's understand frequency okay frequency is actually the number of oscillations the number of oscillations in per second this doesn't make anything clear okay what if let's say that you have I I give you two biscuit packets one is Oreo one is Mari biscuit which one would you like to eat more everybody together we love Oreo right great amazing yes we all love Oreo biscuit right nobody likes Maria it's only for diabetic patients that's what we say even I used to say this my parents have diabetic but I still used to say that only you guys eat it I'm not gonna eat it right so anyway everybody likes Oreo just for stereotypically we are saying some of you might be like ma'am who said that I like but who said that I like good dish sure but just understand Oreo and Mari two options we will all go to Oreo biscuit no both the biscuit packets so I have given you let's say two biscuit packets one Oreo biscuit packet one Mari biscuit packet both of them have 10 10 biscuits in it okay both of them have 10 10 biscuits in it now what if I give you five minutes and I say that finish both of them five minutes you gobbled up you're eating like that and Mario can't eat can't eat now what did I say I said five minutes how many Oreo biscuit did you eat 10. you ate 10 Oreo biscuit in five minutes right five minutes 10 Oreo biscuit that means in one minute you have eaten two Oreo biscuits but when it came to Mary biscuit you were like oh my God so in five minutes you have eaten let's say five biscuits that means that in one minute you have only eaten one biscuit so which one did you eat more you ate the Oreo biscuit more so what is the frequency in one minute how many biscuits did you eat one minute how many biscuits that you ate is the frequency of eating your biscuits the frequency of eating Oreo biscuit is two in one minute the frequency of eating Mari biscuit is one in one minute same like this number of oscillations now not one minute number of oscillations in one second so how many times did the wave you have seen a wave right what is the wave the wave is usually like this and this and this and this right so how many times did the wave come like this and then went like this came like this and went like this so basically this this this this this this this in one second how many times did it this happened that's your frequency I messed up my speech big time anyway so frequency is denoted by Nu and what did I say it's number of oscillations yes in one second okay next comes wavelength what is wavelength wavelength is given by something called as Lambda what is wavelength wavelength is basically see if I make a wave like this okay this this this this the distance between this peak to this peak the distance between this peak to this peak this is called as wavelength so I can write distance between two consecutive Crest these are called as Crest and this is called as draw okay the the bottom Peaks are called as straw t-r-o-u-g-h and this is called as crest cool guys okay so the distance between two consecutive crest or close that's your wavelength all right all right yes now we come to something called as amplitude what is amplitude amplitude my dear students look here look here look here look at this is amplitude the maximum distance from the rest position the maximum distance from the rest position or the height of the crest okay let's write it down what is amplitude the maximum distance from the rest or mean position let's say okay mean position is amplitude or we can also write it as height of crest or depth of true got it all right moving on now next what is the next one next one is velocity what is velocity here velocity is speed of light okay my dear students what is velocity here the velocity electromagnetic radiation they travel in with a velocity of that is speed of light 3 into 10 to the power 8 meter per second all right got it okay now there is something called as wave number wave number is a nothing but inverse of wavelength what is it inverse of wavelength thank you foreign all right everybody yes now what is important is that in in vacuum all types of electromagnetic radiations okay regardless of the wave neck they all travel at the same speed in vacuum all of them they travel in the same speed and that is your speed of light 3 into 10 to the power 8 meter per second got it yes so here is a Formula what is the formula my dear students the formula is everybody I'm writing it here with blue that is C is equal to what is it C is equal to V into Lambda this is the formula so C speed of light B is velocity and uh V is velocity only no V is velocity of light that is C sorry not not V this is frequency sorry this is new this is new okay not V yes frequency wavelength this is frequency this is wavelength and this is speed of light cool so this formula is important all right now moving on this is how your electromagnetic radiation looks like okay now what is happening here see from so this side what is what you have is energy is the most here okay at the extreme left side of me extreme left side here the freak the energy is the highest okay energy highest okay and this side wavelength High okay so basically from this side to this side wavelength increases and from this side to this side energy increases all right yes okay and this is your visible region so it starts from actually it starts from cosmic rays but you can forget cosmic rays because it's not there in your ncrt you can start with gamma rays x-rays ultraviolet infrared radio waves okay and in radio waves you have radar TV FM all of this okay how do you remember it you can remember it as gamma XUV yes x u v x ray then here there will be ultraviolet also Ultra UV right ultraviolet then visible so gamma XUV infrared radio gamma XUV infrared radio that's how you can remember it so electromagnetic radiation till here we have understood now let's understand that how do objects behave when they are you know when they are introduced to electromagnetic waves now there is an object called as black body radiation I know I know in the charge you are all going to like winter black winter black winter black I know I know so people have started speaking about winter black and all of these right and what is black body radiation guys what is black body radiation basically if we have an ideal body doesn't exist if we have an ideal body which can emit emit means produce it can produce and absorb radiations of all frequency uniformly whatever is the frequency whatever is the number of oscillations it can emit it can take absorb it and it can emit them uniformly that's called as black body and the radiation that is emitted by not emitted the radiation that is emitted by such a body or such an ideal body is called as nothing but black body radiation so a black body is actually is in thermal equilibrium with its surroundings thermal equilibrium right with its surroundings so the surrounding and this both of them have the same heat energy right it radiates the same amount of energy per unit area and it absorbs also the same amount of energy from the surrounding at any given given point of time that's what we think right now from here we move towards Planck's quantum theory what a plan do now plants said that you know what guys forget about all of these forget about all of these let me explain you something it can't be just wave way way wave that you're talking about because classical mechanics actually could not explain a lot of things right so he told he came up and he said that he gave the name quantum what is quantum Quantum is actually the smallest quantity of energy that can be emitted or absorbed in the form of electromagnetic radiation and the energy e of a Quantum and a radiation is actually directly proportional to the frequency and that's when we say that e is equal to H mu but that we will come to later so now understand what he said he said that different atoms and molecules they can absorb and or they can emit energy in discrete quantities they are not going to absorb it in ways they are going to observe it in discrete quantities you know small packets you just like how you did it with biscuit right you can't put the whole you can't put the whole biscuit packet in your mouth right you took one discrete two discrete three discrete it wasn't like ah it wasn't like you just opened your mouth and biscuit was just going in in continuous wave like function no discrete one two exactly that's what blank said so the smallest amount of energy that can be emitted or absorbed by observed in the form of electromagnetic radiation that is my dear students called as your Quantum and he said that the energy of the radiation absorbed or emitted is directly proportional to the frequency of the radiation which means that basically he said nothing but he said e is equal to e is equal to what h and new new is the frequency what is this H this H is the Planck's constant what is it the H is the Planck's constant gotcha yes okay so he said that energy of photons how do you calculate the energy of proton proton energy of photon is proportional to frequency e is directly proportional to Nu so if you have to remove the proportionality constant what will you do you will write it e is equal to H Nu so the constant of proportionality is called as Planck's constant now that H Nu we have written right H Nu we also know that H Nu can be written as H C by Lambda and that's exactly what you have written so e is equal to H C by Lambda yes e is equal to HC by Lambda because Nu is equal to C by Lambda remember that formula this formula Nu is equal to C by Lambda so from here HC by Lambda HC by Lambda we can write it right so C speed of light Lambda is wavelength and H is Planck's constant got it yes okay all right now all of this is done now comes another topic called photoelectric effect what is this photoelectric effect so in 1887 there was someone called herds there was someone called Hertz h e r t z I'm not liking the blue color anymore so let me take green color his name was h e r t z Hertz in 1893 1887 sorry in 1887 he performed in beautiful interesting experiment okay and in that he saw that electrons were being ejected that if electrons were coming out when you take certain metal when you take certain metal and when you expose them to a beam of light your Shining Light and you have taken a metal Shining Light is Shining Light is hitting the metal and electrons are getting ejected electrons are coming out of it okay this phenomena was called as photoelectric effect so let's write it down yes Hertz in 1887 performed an experiment foreign that electrons were ejected when certain metals were were exposed to okay exposed to a beam of light and this phenomena okay this phenomenon is called as photoelectric effect understood everybody got it clear amazing now what were the results what were the results of this experiment he saw that the electrons were rejected from the metal surface without any lag there was no lag as in the Moment The Light Beam hit electrons ejected the moment the light beam hit electrons were ejected there was not a second of a lag between the two incidents okay that's what is written in the first point cool now it says that the number of electrons that were ejected it is directly proportional to the intensity or brightness of the light how bright the light was on that it depended okay and for each metal there is a characteristic minimum frequency called as V naught also called as threshold frequency what is this threshold frequency so understand this uh you know let's just do let's just say that okay so this is my skin right I'm going to pinch myself right I'm going to pinch myself I'm going to pinch myself I'm going to pinch myself it's not paining it's not painting it's not painting and then suddenly I do this oh we did pay so when did that sound it came when did it come when did I produce that sound from my from my mouth not in the beginning in the beginning I was able to take it in the beginning I was able to take it so there was a threshold there was a point at which I felt like oh this is paining that is called as threshold threshold can be very easily understood in in a Layman's song as Benchmark like that's it after this I will start reacting in a different manner all right got it okay so that's your threshold frequency so there is a frequency below which you will not be able to see the photoelectric effect you will not see only after you have reached the threshold frequency only after that you will be able to see the photoelectric effect okay got it so threshold frequency is Nu naught and this is your new your frequency has to be higher than the threshold frequency for you to be able to see the photoelectric effect you get it yes and then the ejectorate electrons and the ejected electrons they come out with kinetic energy obviously by velocity if there is velocity there is kinetic energy right and the kinetic energy of these electron it increases with increase of frequency of the light use U yeah got it cool now moving on photoelectric effect We are continuing photoelectric effect Only The Moment I Saw The Heading it came in my mind that let's say it again photoelectric effect anyway so now everybody everybody was you know Going Bonkers about it that what is this this is a new thing we were all talking about wait wait wait and then suddenly somebody comes and no there is packet of energy no this is called as quantum so then comes Einstein I was like Einstein was like I will tell you I will tell you so everybody was like sure go ahead so Einstein said that the frequency of the incident like what is incident like that like that is falling on the metal surface the light that is falling on the metal surface is your incident light so the frequency of the incident light is more than the threshold frequency we understood and the excess energy H Nu minus H Nu naught is imparted to the electron as kinetic energy understand this so if I have a let's say this is a box okay this is a box correct what did I say I said that the frequency of the incident light so this is the frequency of the incident light the frequency has to be new this body has a frequency has a threshold frequency Nu naught right so when this new hit the box here what happened some amount got absorbed some amount of it got absorbed right but the rest of it was the rest of it was transferred so some amount of it got absorbed and from here the electron came out the electron came out what did this electron have this electron had Nu minus Nu naught still did not get it let's understand it one more time let's say that you are giving 10 okay 10 is the energy 10 is the energy with which the incident light is coming and falling on the metal surface and let's just say that the threshold frequency is 5. the threshold frequency is 5 10 is the frequency with which the light is falling on the metal surface 5 is the threshold frequency so what will this the electron will come out with five the electron will have a kinetic energy of 5 because 10 minus 5 is also equal to 5 no got it 10 minus 5 is equal to 5 that's what he said so how can we write it so the kinetic energy that means the kinetic energy what did I say the kinetic energy is basically Nu minus Nu naught if I write it properly I can write it as half MV square is actually equal to C I have to you you know remove the proportionality constant and everything so it will become H Nu minus H Nu naught or H Nu if I have to find what is the frequency I can always calculate it as H Nu is equal to H Nu naught minus half MV Square not minus sorry plus half MV Square so this is a Formula that is important for us got it yes write everybody understood everyone I can also write it as okay I can also write it let's check it out here age news now can I not write it as HC by Lambda is equal to is equal to HC by Lambda not I can also write it as HC by Lambda naught plus what k e plus k right I can write it like this correct absolutely right absolutely right yes absolutely right okay okay got it everybody understood this understood this amazing all right now what do we have to do so this Lambda naught is now now if I have to find it out okay let me write it down so Lambda naught is basically the threshold web wavelength this is the threshold wavelength cool and what is Lambda Lambda is the wavelength of the incident light easy peasy Biryani tasty wavelength of the incident light yes okay V is the frequency of the light being up sorry not V again new is the frequency of the of the light Nu naught is the frequency of the new naught is the threshold frequency right so everything all is clear all right all is clear now my dear student let's take a look at the graphs of the photoelectric effect let's do that yeah let's do that this right H Nu yes H Nu is equal to H naught Plus H Nu naught plus half MV Square what is the formula the formula that we got here is H Nu is equal to H Nu naught plus half MV Square which means nothing but kinetic energy is that right is that what we got correct half MB square is kinetic energy so that means that so that means that I can also write k e is equal to H Nu naught yes h no sorry not H Nu naught it will be H Nu minus H Nu naught correct check it out check it out check it out H Nu minus H Nu naught am I right now this formula ke is equal to H Nu minus H Nu naught don't you think that it looks like Y is equal to m x minus C absolutely yes it looks like Y is equal to MX minus C right everybody so let's take a look at the first graph now all right yeah so let's do number one graph number one where I'm going to draw a straight line like this a straight line like this these are my x's yes so this one let's draw it kinetic energy yep kinetic energy and what will this be this will be Nu obviously this will be new okay so Y is equal to MX minus C right Y is equal to MX minus C so the first graph is between kinetic energy and Nu that is frequency okay so my graph will be somewhat like this this will be my first graph okay yes now let's do a second graph our second graph will be between number of ejected electron and frequency what did I say it will be between number of ejected electrons versus new okay so how will this graph look like now this graph will look a little bit like take a look at it it will be like this sorry my hands are only not straight how am I how will I ever be able to draw a straight line so like this like this yes where new is here and this is my number of electrons okay this will be like this this is the graph that I will get okay all right now let's do another third graph my third graph is number of ejector electron versus intensity this time okay no more frequency let's do intensity so number of ejected electrons versus intensity if I draw a graph for intensity what will I get this time this time my graph will look a little like how any idea this time is going to be like this yes because as you increase the intensity the number of ejected electrons also increases so this is my intensity all right all right and this is my number of electrons ejected okay now if are we going to end it a third no we're going to do another one yeah this time we're going to do another one okay this time what if I change it my fourth graph is now look here look here look here my fourth graph is between see this was kinetic energy versus new this time let's take new versus kinetic energy okay if that is the case then my graph will look a little like this and then this yes so this is where I'm taking ke and this is where I'm taking new now what will happen now what will happen take a look at this so ke is equal to H Nu minus H naught right that's what I wrote yes that's what I wrote but what if I want to again write it like this like this yes what if I write it as h k e is equal to what will be k e is equal to cello let's let's write it here okay with a different color so k e from that formula I can write k e is H Nu minus H Nu naught is that right that's the formula right does the formula so I can also write it as H Nu is equal to H Nu naught plus K correct yes yes everybody right now what if what if I what if just just take a look at it what if I divided by h on both the sides if I divide it by h on both the sides then my equation becomes new is equal to Nu naught plus 1 by h k e am I right yes and that means that my graph will be somewhat like this where the slope will be equal to 1 by h you getting my point yes and this part will give you new naught got my point yes so these are the four graphs that you have to remember okay these are the four graphs that you have to remember now we come to something called as stopping potential so what is this stopping potential any idea what is the stopping potential guys just a second where is my cursor yeah what is the stopping potential what do you guys think actually just a second just a second just a second okay so basically the stopping potential is the potential that is required from stopping the electrons being ejected you're getting my point okay now comes a topic called as stopping potential what is stopping potential stopping potential is basically the minimum amount of potential that is required to what that is required to stop the photoelectric effect what did I say the minimum potential required to stop the photoelectric effect okay let's write it down to stop the photoelectric effect is called as stopping potential all right everybody yes okay so now of course there will be a formula here also what do you think won't be there a formula there will be yes what is the formula so take a look at it of course we will write it as uh k e is equal to yes k e is equal to Q into V naught we know that right K is equal to Q into V naught once again I said V naught it's Nu naught yes that means that kinetic energy is equal to e into V naught okay all right yes is that what you you get it so this is our minimum potential that must be applied to stop the photoelectric effect clear this is something that you have to remember all right moving on from here we have a question so in photoelectric effect the kinetic energy of photoelectrons increases linearly with wavelength of incident light frequency of incident light velocity of incident light or atomic mass of an element we just did it guys we just did it yeah we just did it kinetic energy of photoelectrons increases linearly with what is answer of course option b frequency of incident lied very good next question electromagnetic radiation with maximum wavelength is do you remember gamma XUV infrared radio wave so what is it going to be and and and what happened was this side energy was extreme that side wavelength was extreme right so radio wave is the one that has the maximum wavelength don't forget it okay next question okay so electromagnetic radiation having Lambda is equal to 310 angstrom 10 angstrom is subjected to a metal sheet having work function 12.8 electron volt what will be the velocity of photoelectrons having maximum kinetic energy okay guys so what is it that we know we know that e is equal to H Nu yes H Nu yes and we also know that this is equal to HC by Lambda am I right we know that yeah now what is h h is equal to 6 point six point what is it 6.63 6.63 into 10 to the power minus 34. right that's our H correct okay C and all all of that you know correct all of that we know now kinetic energy so maximum kinetic energy right maximum kinetic energy right so k e so ke will be what k e we all know that it is half MV Square half MP Square yes yes and that half MB square is basically equal to the H Nu which is basically equal to w W is basically the work done okay half MV square is equal to H Nu is equal to w w is basically 12.8 EV that's given to us 12.8 electron volt that is given to us okay all right now once again we know that HC by Lambda it is so e is equal to 6.63 into 10 to the power minus 34 divided by divided by H C Lambda guys H C so this multiplied with 3 into 10 to the power 8 meter per second am I right yes this is what you will do yes and divided by divided by what is my Lambda Lambda is given to us see 310 and strong okay so let's write it 3 1 0 into 10 to the power What minus 10 because it's angstrom corrector yes so this will be all equal to I think around 10 8 this this is 310 3. okay what will this be equal to what will this be equal to any idea any item no shall I forget it this you can calculate later okay this you can I think uh calculator later you you do this calculation okay all right uh so once you have done all the calculation once you have done all the calculation then let's we also see that W is equal to 12.8 EV that is given to us right so instead of that instead of that what if we change it into Joule if we change it into Joule then it will be 12.8 EV multiplied with 1.6 into 10 to the power minus 19. all right yes 12.8 electron volt multiplied with 1.6 into 10 to the power minus 19. now minus 19 once we do this the resultant will be in Joule okay the resultant will be in Joule got it yes all right so that means that you will get it around 12.8 into 1.6 that means it will be around two point something two point something will be the answer okay now once again if I do half MV square is equal to H Nu minus w yes correct everybody now you know what is your W you know what is your W right correct everybody great you know what is your e what is your e is uh something that you have calculated from here yes from here got it yeah you would have calculated it from here and then M you know is around 9.1 into 10 to the power minus 31 kg correct now when you put all of these you will get V Square you will get V Square okay whatever you get as V Square then what you have to do is V is equal to root over this this okay all right that is what you have to do please calculate it on your own I don't have a calculator I don't want to use the calculator but you can do this much okay you can do this much I'm pretty sure about it all right guys so I think uh the correct answer is option C they're saying the correct answer is option C so what you can do is you can just go back calculate it and then check it out all right now we come to something that is called as boards atomic model this is the beginning of our many many many derivations that we're going to do now okay so Bohr's model of the atom Boar's model of the atom was actually another stepping stone for us right yes after Rutherford this was another stepping stone so Bohr's model of the atom it was proposed by no one else but Neil's board right in 1930 because obviously there were drawbacks that were related to Rutherford's model and Nia's board just wanted to explain the things a little better right so he was the first one who could explain quantitatively the general factors of the structure of what hydrogen atom idea students please do remember it that Bohr's atomic model is great but for hydrogen only for one electron system it is great but not for something else which is why we came up with something else later on right so for hydrogen atom and its spectrum and he used Planck's concept of quantization of energy now see what magic he has created okay what magic he has created so what he said was the electrons in the atom can actually move around the nucleus we all know that absolutely right we know that that the electrons in the atom can move around the nucleus in a circular path of fixed radius and energy yeah absolutely bro we know that great these parts they are called orbits he spoke about orbitzna stationary States or allowed energy state so what are the names that you can call them with what are the names guys the names are check it out check it out check it out the names are yes these parts are called orbits stationary States or allowed energy stage yes now these orbits are arranged concentrically around the nucleus you understand what is concentric this is your nucleus this see this is your nucleus this this this one after another one after another one after another that's called as concentric circles got it got it got it yes this is called as concentric circles all right yes we understand this now moving on from here moving on from here now comes the postulates that means things that it typically or particularly said so he said that electron revolves around the nucleus due to the centripetal force that is provided by the electrostatic force of force of attraction you remember nucleus as positive charge electrons are negatively charged there is a there is a force of attraction electrostatic force of attraction is that and because of this electrostatic force of attraction they have a centripetal force which governs the movement of the electrons great understand amazing yes yes got it now if this is a centripetal force check it out yes what he said is what he said is if this is our nucleus if this is our nucleus and if this is an electron then the electron is being pulled here the electron is being pulled here by who by the centripetal force by the centripetal force the electron is being pulled correct but just equivalent to that there is also a centrifugal force so the centripetal force is the is the electrostatic force that means coulombic Force this is equal to a coulombic force because it's an electrostatic force but this centrifugal force that is the kinetic energy or the electron right are you getting it so this is my dear student that k q 1 Q 2 divided by R and this my dear student is half MD Square both of them are equal getting my point anyway we're coming to it we are coming to it we're coming to it now he said that energy is emitted or absorbed listen to this very carefully he said that what Rutherford said that electrons are revolving revolving revolving their emitting energy energy and then finally at certain point they have lost all energy and they fall into the nucleus and we are questioning the existence of matter now but true but Niels bore said something very brilliant he said that hey hey hey the electrons are moving around the nucleus no doubt about it but is it ready is it emitting energy no when it is moving or when it is revolving around its particular orbit there is no energy emission that is happening the energy emission my dear student is only happening when the electron jumps from a lower level to the higher level or from higher level to the lower level that's when energy gets emitted or absorbed yep that's what he said and that changed the way we look at all of these things so he said that the energy okay from E2 E2 is this to this right this to this this is your E2 minus E1 so in first energy level let's say it's E2 in the second one it's E1 so E2 minus E1 or Delta e the difference in the energy is basically nothing but H Nu or is equal to H C by Lambda make sense only those orbits are permitted he said only those orbits are permitted in which the angular momentum of the electron is a whole number multiple of H by 2 pi okay what did he say he said that MVR is equal to NH by 2 pi where n is equal to 1 to 3 Etc this H by 2 pi H by 2 pi can also be written as H bar okay what can you write it as H bar so you can write it like this also that MVR is equal to NH bar okay and this means that like energy angular momentum of the electron in the atom is also quantized the angular momentum is also quantized not Just Energy but angular momentum is also quanticide now let's derive this whole thing okay so according to bores postulate according to bores postulate we have understood that we have understood that please take a look at it my dear students here please take a look at it I'm gonna do this here so according to Boar's postulate we understand that centripetal force is equal to coulombic force which is equal to centrifugal force right now to start with we have to start with we have MV Square by R is equal to k z e Square divided by R square corrector great all right so what we can cut now from here what we can cut is take a look at it we can cut this we can cut one of the R so that means that our MV square is equal to k z e Square by r Ito yes that means that R can be written as R can be written as k z e Square divided by MV Square am I right am I right and let's call this equation let's call this equation to be number one or equation 1. all right yes now my dear students okay now from both postulate we know that MVR is equal to n dot h by 2 pi am I correct yes we know so how can we find the velocity very easily so V is equal to NH 2 pi r m is that right yes right now let's substitute this value okay let's write it here substitute in equation 1 substitute in 1 what was our one one is R is equal to k z Square divided by m v Square okay k z Square divided by m v square right that is our r if we substitute this if we substitute this in equation 1 okay let's do it yes let's do it everybody substituting in equation one what will we get is this right [Music] um R is equal to k z Square so let's take it here and now let's let's take it here let's take MV Square r so let's imagine that it is MV Square R is equal to k z e Square correct so that means if I put the value of V Square here that means n h 2 pi r m Square R is equal to k z e square right to everyone make sense nonsense makes sense right now what I can do is I can also write it as n Square H Square One M gone here from here also one M will go that means it will be 2 pi sorry not 2 pi it will be 4 Pi now square right here see it is square so that means it will be 4 Pi so it will be 4 pi r Square yes 4 Pi Square R square m makes sense this is equal to r r will also be here R will also be here right R will also be here or R gets canceled oh R gets canceled R gets canceled R gets canceled so this will be equal to k z e Square this is nothing but it's equal to C here n Square H Square divided by 4 Pi square m r is equal to k z e Square make sense everybody getting my point getting it everyone amazing so now from here what I can see is if I cross multiply then what will be my R what will be my r from here I am taking it here yes I don't want to bend too much and write it okay so check it out so my R will be equal to what will be my r equal to my R will be equal to n Square H Square divided by k z e Square Pi Square M and 4 yes is that right 4 k z Square Pi square m this is the this is the formula for radius what is this this is the formula for radius okay do not make a mistake here please do keep writing it down while I'm writing it everybody while I'm writing it please do keep it one second where is my cursor again yeah that's this is where found it found it found it found it found it okay now what we can do is now check it out check it out check it out now what we can do is let's put the values okay let's put some values here let's put m is equal to m is equal to 9.1 into 10 to the power minus 31 kg correct yes what is h h is Planck's constant you know that also H is equal to what 6.626 into 10 to the power minus 34 yes yes very good Pi forget about it K is 9 into 10 to the power 9 yes K is equal to 9 into 10 to the power 9 yes everybody and what is e is equal to 1.6 into 10 to the power minus 19. am I right yes if you put all of these values in this you know what you will get you will get R is equal to there is a number please do remember the number the number is 52.9 what is the number 52.9 so only keeping the very variables here 52.9 into n Square divided by what will you keep atomic number Z in picometer okay after all of these you will get this value into picometer so please remember there is if you want to solve problems directly you have to remember this you can also remember this derivation if you want to it will be great for your J advanced level Julio all right now once again everybody let's move forward okay let's move forward I had to I think write it here also but yeah I think you you get it right I think you get it okay chill now let's do it from boards postulates once again what do we know MB R is equal to nh2 PI right right okay got it and we also know now that R is equal to n square a square divided by what is it n Square H Square 4 Pi Square k z e square m right this is our R correct yes so let's keep this to be equation one and if we keep this to be equation two what will we get down if we put the value of R in equation 1 let's put R in equation 1. if we put the value of R in equation 1 do you know what we will get we will get velocity we will get velocity but let's do it okay what is our R okay so we have m v and R is my dear student let's write it in a bracket so that we don't get confused n square a square 4 Pi square m k z e Square am I right this is our R yes is equal to n dot h by 2 pi so H cancel H cancel n cancel n cancel 2 cancel 2 here remaining Pi 1 cancel Pi 1 cancel right so this side only K is remaining that means that m v in fact M cancel here 1 M cancel okay so this will be equal to V n H divided by 2 pi k z e square is equal to K correct but this I can change it this side so V will be equal to V will be equal to K Square 2 pi K Square z e Square divided by n h make sense makes sense so this is your velocity formula this is your velocity formula get my point guys this is my velocity formula okay all right so putting the value of k e now now what you can do is if you put the value of k e and H you know what is K 9 into 10 to the power 9 you know what is e 1.6 into 10 to the power minus 19 you know what is X 6.626 into 10 to the power minus 34. if you put all of that you will get a velocity constant value that is 2.18 into 10 to the power 6 Z divided by net only variable thing is z and n z and N are the only variable and here you will get velocity in beta per second here you will get velocity in meter per second got it got it got it got it got it this makes sense right this makes sense right everybody great okay now okay now moving on from here moving on from here do we also want to find out the energy guys I think so I think so right we do okay okay now let's do it for energy okay let's do it for energy let's find out the energy so how will we figure it out so total energy of an electron that is revolving in uh what in a particular orbit guys yeah so let's write it down that total energy of a particular electron of an electron let's write yeah what particular and all why make it long of an electron revolving revolving in a particular orbital now let's write particular in a particular orbit because there are a lot of orbits correct in a particular orbit is what is it we know that total energy is equal to definitely kinetic energy plus potential energy correct to great what is kinetic energy half MV Square what is kinetic energy half m v square right but now we know that from boards postulate from boards postulate from both postulate what do we know MV Square by R is equal to kze square divided by R square remember that yes absolutely yes we don't remember it MV Square by r e mistake mistake mistake happened here MV Square by R yes MV Square by R is equal to k z e Square divided by R square R square only no R square okay so what will we get we will get R will cancel R we will cancel so what will we get here so MV square is equal to kze square that means we know that MV square is equal to k z e Square by R correct that this value don't you think that this value we can put it in this equation correct we can do this yes we can put this value in this equation yeah so what we will get our kinetic energy will be equal to check it out check it out check it out will be equal to k z e Square by 2R makes sense nonsense yes no yes great okay this we understood now what about potential energy that also we will have to figure it out yes so how do we calculate our potential energy let's check that out as well let's check that out as well okay now what is our potential energy our potential energy as far as we know we know that potential energy is always equal to minus of minus or half minus half of K right potential energy is always minus half of K do I potential energy is this minus k z Square divided by r okay all right yes so our total energy becomes okay total energy we know we already know that we already know that what happens is potential energy is equal to minus half of let me just write it down here okay p e is equal to minus half of k all right this is what we know because we know this so we can write directly that p e is equal to not minus not minus it was a minus I think it was twice and it was twice yes yes yes yes yes I think I made a calculation error just now just a minute just a minute just a minute yes yes absolutely yes absolutely yes what I did was huh because this is 2R right this is our K so it cannot be minus half it has to be it has to be just a minute it has to be minus 2 minus 2K so if I put 2 into this then the two gets canceled right yeah so p e will become minus k z Square divided by R okay all right p e will become minus k z Square divided by I so my total energy will be k e this this part is my kinetic energy this part is my kinetic energy plus Plus even if I write plus here this is still minus so minus k z e Square divided by R that is minus p yes now you might be thinking that Mom how does this happen how does this happen what is our K guys check it out check it out what is that K our K is k z e Square divided by 2 R minus yes minus k z e Square divided by R so if I take the LCM my LCM will be 2R so this will be k z e Square minus now 2 will get multiplied here so 2 k z e Square now if I minus it then what will I get I will get minus k z a square divided by 2R make sense see this is exactly what you're getting here right this is exactly what you are getting here got it yes now we know that now we know that R is equal to what now we know that R is equal to n Square H Square divided by 4 Pi Square m k z e Square this is our r so if I put that if I put that okay now if I put the value of R in our te here yes if I put the value of R in this case then what will I get check it out minus k z e Square divided by 2 into n Square H Square divided by 4 Pi square m k z e Square this yes which means that this is equal to all of these will go up here now but just this this gets canceled here okay so it will be minus K Square Z square e to the power 4 yes then it will be Pi Square here will be a 2 divided by n Square H Square and that is your total energy this is your total energy remember this as well this is also a value that you will have to remember cool yes so from all of these here okay I was right only oh no yeah I was right yeah see k e plus P yes so minus K is equal to half of P yes and p e is equal to potential energy is equal to minus of 2 k and t is always equal to total energy is equal to minus of kinetic energy all right these are the things that you know now energy of electron in bores orbit it continues a little bit more it continues a little bit more it doesn't get ended here only so let's take a look at this also yeah now if I put the value off so total energy you saw let me write down that formula again right let me write down that formula so we know that total energy is equal to it's a huge formula huge formula here see minus 2 what is it K Square Z square e to the power 4 okay K square e to the power 4 Z Square then Pi Square Pi Square divided by n square a square correct this is your formula so now if you put the values of k e and and and H right if you put all of these value now we will once again get a constant formula where total energy is equal to my dear student minus 13.6 and what are the valuable what are the variables Z and n z and N so it will be minus 13.6 into Z Square by n Square this will be in in in in in what will be the value uh so what will be the unit it will be electron volt per atom this is also something that we will have to remember great understanding everybody yes so this is the formula sheet that I have given these are the things that you have to have to have to remember for your calculations this is the total energy minus 13.6 Z Square by n Square electron volt per atom potential energy is 27.2 z Square by n Square EV per atom kinetic energy is once again 13.60 this is minus 13 this is 13.6 Z Square by n Square radius of nth bore atom in the exam whatever they give you one yes first second third fourth you will be able to calculate it with this formula RN is equal to 0.52 and what is n n is this number yes n Square divided by Z in angstrom you will get it velocity of the electron in nth orbit these are the things that you should print it out and keep it in front of your table and remember it every single day I'll give you the PDF in the telegram Channel please do join the telegram channel so that you get the PDF and then you will not have to study at all you also have the energy one energy to energy three energy four energy five all of this I have given to you okay now let me take a break and let me drink some water you should also drink some water drink it up thank you all right all right okay so now moving on from here there were certain bit of limitations nothing in the world comes without limitations there were certain bit of limitations the limitation was that he could not explain the line Spectra of atoms which contain more than one electron so Bohr's Atomic bores a model of atom is very limited to one electron system okay it's very limited to one electron system that is n a 10 plus H hydrogen right basically anything that looks like hydrogen li2 plus is where it is limited okay next is that he could not explain the presence of multi-spectra lines he could not right Bohr could not explain the debris concept of dual nature of matter so all this time Einstein said that let me tell you it is particles yes before that everybody was like wave and then Debra came and he said that no no no no no it's dual it can behave like a wave it can behave like a particle yeah so Bohr could not explain the splitting of spectral lines in the presence of electrical field Stark effect and magnetic fields semen effect this also I'll write it down for you and I'll explain it he could not explain Heisenberg's uncertainty principle so that means from all of this we understood that we have to read now debroy we have to read Stark effect Seaman effect and we have to read Heisenberg's uncertainty principle now coming to hydrogen Spectrum okay what is this hydrogen Spectrum understand this that the line spectrum of hydrogen atom was observed by bomber and that's why the first spectral line that you see in your ncrt is what bomber yes Lyman bomber posture bracket fund all of that you see right but the first one was actually observed by bomber first okay bomber observed that in 18185 1885 and he saw that hydrogen gas at a very low pressure taken in a discharge tube yes and the light emitted on passing the electric discharge is examined with a spectroscope the spectrum that is obtained is called as emission spectrum of hydrogen now here you see there are two two Spectrum right you must be thinking that Mom what is this what is this so this is hydrogen absorption spectrum and this is what is called as emission spectrum emission is something that is emitted that is given out and absorption is all the things that is absorbed by it now take a look take a look this absorption and the emission spectrum do you see any similarity there is if you look carefully there is all the places where you see there is black is where you get to see a light here in the emission see black and light here black and light here black and light here that means that the absorption spectra and the emission Spectra these are complementary yes these are complementary so if this happens this will also happen if this happens this will also happens so whatever is absorbed up whatever is absorbed as me understand it so wherever you see black is actually the wavelength that was absorbed by hydrogen and here what you see are the emitted Spectra so what balma saw was emission yes what Bama saw was a mission so basically what he did was he took a tube he took a tube where there was hydrogen gas and there was a lens right just the normal lens that you use in your uh the concave lens basically the concave lens that you use in your uh Physics laboratory then there was a very thin you know a thin narrow slit was there you remember in physics you will do this experiment called as Young's modulus later on but anyway uh so a very thin narrow slit is here and then from here when the light has passed through another lens and then through another prism you see the emission Spectra okay you see the emission Spectra cool guys yeah all right now you see that there is lime in Spectra there is balma Spector so bomber what bomber saw did you just notice that there were different colors there was Violet there was Indigo there was blue there was there was there was blue here again and then there was red also so these were the lines that bomber saw right so bomber saw something that is invisible Spectra Lyman saw something in ultraviolet Spectra pastion saw something is infrared after pastram there was another there were another two right fund and bracket and then there was another one called as Humphrey okay Humphrey Humphrey you don't have to study though it's not there in your book right so you will only study from Lyman bomber passion fund bracket okay these are the ones fund was also in infrared bracket saw a bracket also saw it in infrared and Humphrey was in uh far infrared yes far infrared that's what he saw okay now what happens is there is something called as rydberg's equation this is this is one equation that you have to have to have to remember even if you forget your name even if you forget your Ja Rule number but please don't remember don't forget this because from here questions definitely do okay so one zero nine six double seven into Z Square then you know what is z is the atomic number n one square what is N1 N1 is n c n 1 square n two square yes so when electron jumps from N2 to N1 see from N2 to N1 it is lime in series yes when it comes from okay this is where we have made a mistake here N2 to N1 everywhere it is written is okay so when the jump is only one right when the jump is always to one yes it is called as Lyman series when the jump is always at 2 N is equal to 2 see do you see n is equal to 2 it is bomber series when the jump is always n is equal to 3 it is Passion series after that it is bracket and after that it is fund okay so I said it fund bracket it's bracket fund okay it's bracket fun got it everybody yes now once again guys from Bohr's postulate we have to do another another what we have to do another another solving okay let's do it guys let's do it one second this is why ha so once again from Boar's postulate we know that Delta is equal to E2 minus E1 is which is equal to H Nu is equal to H C by Lambda correct now we also know that H C by Lambda is equal to E2 minus E1 which is equal to minus 2.18 into 10 to the power minus 18 Z Square by n Square n 2 square minus this so basically this is what is given to you right now from here okay from here please please please check it out please check it out yes this is what is given to you now from here what we will do is what we will do listen I hope you are all focusing here okay I hope you are all focusing here so from here what we can do is red yeah keeps happening anyway where was I it's C by Lambda is equal to E2 minus even yeah so HC by Lambda is equal to E2 minus E1 is equal to minus 2.18 into 10 to the power minus 90. correct but do I also see that do I also see that this is also minus two point 10 to the power minus 19 this is also minus 2.18 into 10 to the power minus 90. now don't you think that I can also take Z Square here as common Z Square also if I take it as common yes now what I can do is check it out I can do 1 by n 1 square because this is minus this is minus so plus yes then minus then minus because here is a minus sign here is a minus sign so what I can do is 1 by n 2 square makes sense nonsense make sense one more thing that I can do is see I can also write it as 1 by Lambda is equal to 1 by Lambda is equal to if you remember it is new bar which is equal to which is equal to what will it be what will it be check it out 2.18 into 10 to the power minus 18 divided by HC can be taken here right I can take the HC here because I was trying to find 1 by Lambda this multiplied with this multiplied with Z Square obviously because Z square is here Z Square then 1 by N1 Square minus 1 by N2 Square makes sense make sense everybody great now what I can write it as 1 by Lambda is equal to Nu bar equal this whole part do you see this is constant this is constant this number is constant so that means that I can write that to be RH which is nothing but this which is nothing but Redbox constant yes so r h into Z Square divided by 1 my 1 by 1 n 1 square minus 1 by N2 square and this is nothing but your red box constant which is which is cello let's write it down here foreign one zero nine six seven seven got it yes that's it that's it we are done with this okay now just remember that this is this is something that you can't remember if N1 is 1 yes the the bottom line is one and then N2 can be 2 3 4 right for bomber it is two always in the second line so three four five bomber is invisible passion is three four five six infrared bracket is also infrared fund is also infrared I'll show one more thing did you note is that right here it has a lot of Gap has a lot of but then as you go up the Gap is reducing and reducing and reducing do you know why because because right here the energy gap is a lot the energy gap is a lot yeah but at this place the energy gap is less and as you go up Indra in the infrared region the energy gap goes on reducing okay now do you want to find out that these are see so many lines are there right one two three four one two three four five there are five lines here here there are only one two three lines how can we remember how many lines are there so the total number of spectral lines you can find it with a formula and the formula is Delta n that again in bracket Delta n plus 1 divided by two and what is Delta n n 2 minus n one whatever is your N2 just subtract that from N1 for Lyman your N1 will be always one right for bracket your for for for bummer your N1 will be always 2 okay so the total number of spectral line during any transition means the number of Maximum possible spectral lines if an electron makes a transition from one energy state to another energy State got it take a look at look at it okay man right it's written here man so from man we can remember that the splitting of spectral lines from here we can remember that the splitting of spectral line in magnetic field got it and start who can we remember when we say Stark do you remember Robert Downey Jr Mr Stark Avenger yeah so start he used to do a lot of electronics things and stuff right so we can remember that the splitting of that's it all right now we come to Deep Roy so what did Deborah say Deborah basically said that according to him the wavelength of a moving particle of mass m with velocity Nu is given by Lambda is equal to H by MV what is MV MV can also be written as c m v is equal to P what is PP is momentum what is this this is momentum m is mass V is obviously velocity yes yes V is obviously velocity so what is rho c m is mass of the mass of the particle base velocity and P is momentum that's what he said now Debra says that according to debris de broy the circumstances of the nth orbit is equal to n times the wavelength of electrons so basically see if n is equal to 3 there are three ways do you see if n is equal to 4 there are four waves do you see if n is equal to 5 do you see there are one two three four five five waves if n is equal to six then one two three four five six six waves gotcha his point it looks very complicated nothing but nothing much okay all he said that circumference of the nth orbit is equal to n times the wavelength of the electron so basically circumference is what 2 pi r 2 pi r is equal to n Lambda that's all he said 2 pi r is equal to n Lambda that's all now let's find out the relationship between the kinetic energy so Lambda is equal to H by MV we know that you know that I know that correct yes this is let's say equation one now my ke kinetic energy is equal to obviously half MV Square let's call this equation number two works works what let's do is now let's Square the equation 1. if you square the equation 1 you will get you will get Lambda square is equal to 8 square by MV Square am I right yes MV Square as in this right H Square by MV Square so that means that m v Square actually it is M Square V Square actually it is M Square V square but let me not write that let me write here MV Square okay so if I write m v Square so MV Square will be equal to let's say that H Square divided by divided by Lambda square and M right now let's call this equation let's call this equation to be 3. okay all right now what do I have I have k e is equal to half MV Square so I can write 1 by 1 by 1 by 8 square divided by Lambda square m which is nothing but am I right this is my k this is my key right oh what did I do I had to write half MB Square oopsie Daisy honest mistake guys honest mistake see one thing you make a mistake and the whole thing goes for a toss anyway it has to be just a minute just a minute just just ha so K is equal to half MV square right so we'll write half and then 8 square by Lambda square m correct this is our K right this is our k this means that I can also write Lambda square is equal to if I take Lambda here then my Lambda Square will be equal to H Square by 2 m k e yeah so Lambda Square will be equal to 8 square divided by 2 m k yes so that means that my Lambda will be equal to root over H Square divided by 2 m dot okay yes and that is the relationship between wavelength and kinetic energy okay so let's start with the first one the first one was obviously we wrote it here somewhere this Lambda is equal to H by P okay Lambda is equal to H by P let's write it down here number one is Lambda is equal to H by P correct which is nothing but H by m v and P is equal to MV right so we know that now we know that P is equal to MB so second formula becomes Lambda is equal to H by m v what will be the third formula guys what is the third formula the third formula is Lambda is equal to root over H Square divided by 2 m k e that's something that we just recently did okay all right yes if it is 2 MKE that means that I can also write it as Lambda is equal to root over 8 square divided by 2 m chest thing what is k Q multiplied with v absolutely QV makes sense nonsense yeah all right now what else what else what else what else what else q v also gives you potential difference if you remember QV is kinetic energy is equal to QV QB is your potential difference V is your potential difference okay now for electron for an electron if Lambda is equal to let's do this Lambda will be equal to 12.24 divided by I hope this is right is this it no this has to be root over yes next Formula what is our next Formula next Formula is 2 pi r circumferences is equal to n Lambda don't forget that 2 pi r is equal to n Lambda right yes n is the number of wave number MVR is equal to n h by 2 pi and all of that you can do if you solve it you will get it right okay okay okay we are almost at the end of it guys Heisenberg's uncertainty principle what did Heisenberg said he what did Heisenberg Heisenberg say he said a very amazing thing and the thing was that the exact position and the momentum of a very fast moving particle cannot be calculated precisely at the same time amazing no what is it he said that we can never determine the exact position and the momentum of a fast moving object at the same time and that is why we have written that Delta x dot Delta P what is Delta X Delta X is basically Delta X is basically the position okay this is the position right what is this this is the momentum it is always greater than or equal to H by 4 pi got it got it h by 4 Pi that's that's what he said okay now what is Delta P we know that Delta p is what m m is mass mass is mass is something that where there is no difference where we cannot put a Delta there right so we will put Delta with velocity MV MV is the one so we'll put m in M multiplied with the Delta V that is also equal to H by 4 pi here Delta X is uncertainty is position Delta V is uncertainty in velocity gotcha great understood understood absolutely understood yeah now tell me something tell me something tell me something can I also modify it a little bit and I can write it as Delta X dot Delta p and then and then if I multiply and divide it by delta T then what will happen If I multiply and divide it by delta T don't you think that I will get a Delta e dot delta T understand what I'm saying okay what I'm saying is so this is this is my normal this thing right yes From Here If I multiply and divide by delta T I will get something like delta T into Delta X into Delta P divided by delta T is equal to or greater than H by 4 PI right if I take it like this then I can write this T dot uh T dot position time into position yes time into position and then momentum by T right T delta T dot Delta Delta x dot Delta P by delta T correct yes so that means that that means that I can also write it as for delta T dot Delta X okay delta T dot Delta X it can be again greater than or equal to H by 4i which means that nothing but this is delta T into what am I saying delta T okay that means uncertainty and energy uncertainty in time will also be equal to H by 4 Pi this is also something that you can write yes just remember all of these guys just remember all of these okay all right just remember all of this great now we have come to something called as principle or oboe rule what did Robert say he said that you have to fill the lower energy first okay what did he say he said that you have to fill the lower energy first filling off lower energy first feeling lower energy first or basically he said that until and unless you haven't okay until and unless you haven't uh done done basically uh actually you know what I'm forgetting something I think I wanted to say something else also here which I've forgotten uh um I possibly haven't said it I just wanted to check is it something that I missed out on ah can't remember anyway forget it let's let's I don't think I have forgotten something anyway we'll we'll see if we have missed out on something okay anyway so uh filling out the lower energy first basically what he means to say is that until and unless you haven't filled this you can't jump here so until and unless I haven't stepped on the number one staircase do you think that I can directly jump to number 10 I can't if I have to climb the you know levels then I'll have to climb one two three four you even cannot jump like without doing your class 11th do you think that you can directly get into J no bro not happening not happening at all you have to tell the lower energy first okay so that is why first one is then 2s then 3s then 2s then 2p then 3s yes then it is what 3s then 3p then 4S then it is 3D 4 P 5S so basically let me just write it it is actually 1s 2s 2p 3s 3p yes then 4S 3D okay 4S 3D correct okay please do remember it after 3D it is 4p okay after 4p it is 5S after 5S it is now what no 4p then 4D I think I'm writing it correct no 4p 5S then 40. I was right okay after this you can just write it down from here okay after this you can just write it down from here now what is hoon's Rule hoon's Rule says that electrons filler subshell singly they will never pair up first first they will go for single single single and only then they will start pairing it up so if you can see it here if you can see it here for 2p if there are let's say if there are two P three electrons then how will you fill it will you fill it like this see 2p3 right will you fill it like this wrong you will not fill it like this will you fill it like this no you will not the correct way to fill it will be for 2p it will be one two three so basically one two three like this okay but if it is let's say 2 p 4 how will you start filling up now it will be one two three so one two three and three this this is how you are going to fill it okay so just make sure that you are not making a mistake here be very careful okay what is polyester rule Polly said that no two electrons can have all the same four quantum numbers what did he say he said that no two electrons oh can have the same quantum number same all four quantum numbers okay uh let's it's very important can have the same all four quantum numbers you're going to ask me remember what are quantum numbers so let's go read that also what are quantum numbers which are quantum numbers are okay now you see there is written something written so the first one here this is called as principal quantum number okay this is called as principle quantum number okay yeah so this will give you the energy shells like K shell L shell M shell L shell right so n is if it is 1 then it is K shell a n if it is 2 then it is L shell n is if it is n if it is 3 then it is M shell and N if it is 4 then it is L shell right so it will be k l m n n n and shell it will be okay Angel right now comes L what is this L this L is called as the muthal quantum number what is it called as azimuthal quantum number this value the value of s a muthal quantum number goes from goes from Plus n minus 1 no no no no no no no no no I think I made a mistake one second one second one second no no no no no no no just a second L goes from L goes from yeah zero two continue continue continue to n minus 1. this gives you the sub this gives you the sub shell I'm a Bengali please excuse me sometimes shab comes in but yeah it's sub shell okay this gives you sub shell or sub energy level so it starts from zero and goes to n minus one so if it is it starts with 0 and if we are talking about the principal quantum number two n is equal to 2 that means it will start from 0 2 it will go to 1. if principal quantum number is 3 then it will be 0 1 2 okay if principle a quantum number is a 4 then it will start from it will start from zero then it will go to one two three all right that's it done now we come to ml ml is the magnetic quantum number ml is the magnetic quantum number this starts from this starts from minus n yes minus L2 plus l foreign it starts from minus L to plus L all right and then the final one is Ms which is called as spin quantum number okay spin quantum number it can only have two values that is plus half or minus half that is how the electron is revolving so the electron can either revolve like this or it can revolve like this okay this is what it is telling that means in one orbital in one particular orbital either the electron can rotate like this or it can rotate like this okay done everybody yes and from here if you know all of these you can actually count the total number of electrons yes you can count the number of electrons You Can Count which shell it is in everything can be counted from this quantum number okay now we come to shape of the orbital the first one here this is your s orbital s orbital has a sphere shape okay this is your s orbital s orbital has a sphere sphere shape this is your p orbital p orbital has a dumbbell shape what is the shape the shape is dumbbell shape okay dumbbell shape cool then comes D orbital the D orbital here is double dumbbell shape this is your D orbital and the D orbital has a double dumbbell shape all right and then F orbital looks even more complex we do not know what shape is it is so we are not going to talk about it right now okay and then final lap of this chapter oh my God I'm so tired but yeah let's let's continue let's let's complete this yeah we're not gonna wait we're not gonna waste time so quantum mechanical model let's continue with this so here what happens was there was this person called shortinger Schrodinger's cat you remember all of that yeah so Schrodinger said that he derived an equation which describes the 3D wave motion of an electron yes now we will not be we will not die dive too deep into this but just remember this equation d square PSI divided by x square plus d square PSI divided by d y square plus d square PSI divided by d z square plus 8 Pi square m divided by 8 square e minus B PSI is equal to 0. okay so basically what is it it's a double partial differentiation you know that right in mathematics you will be doing it differentiation is one thing there is partial differentiation yes and then there is this is what double partial differentiation okay yes so x y z what is this x y and z x y and z are the Cartesian coordinates you know what is Cartesian coordinates so if I make it like this then this point will be your X Y and Z correct yes that's it great what is M here m is the mass of the electron what is e is the total energy of the electron what is VV is the potential energy of the electron H is the Planck's constant this is the Planck's Constant and PSI is the wave function of the electron PSI is the wave function of the electron now this is all in x y z right if I take this if I take this into Polar coordinates there is also something called as Polar coordinates you will again learn about it in mathematics if I take it in polar coordinates yes I will get something called as R Theta and Phi okay instead of x y z this time I will get as R Theta and Phi so when I put this polar coordinates here and if I solve it for e and V if I put different different values of e and v e and v e and V then I will get different values of PSI like PSI 1 psi 2 PSI 3 and dot dot yes now in mathematics have you ever seen that when a result comes and you are not able to solve the root and it looks very stupid it is not satisfying anything correct exactly so some of those values some of these PSI values will be absolutely you know it'll just be stupid it will not make sense but there will also be some of those values that will not be stupid that will actually be meaningful that will make sense to us and those values are called as eigen values what is it called it is called as eigen values you get it these are called as eigenvalues all right everybody getting it yes okay yes amazing now what will happen is C what is the significance of PSI what is PSI giving us right so let's read it the wave function may be regarded as amplitude function expressed in terms of coordinate so basically this wave function this side you can understand it as the most probable function or the amplitude so when you make that wave you understand that there is a peak of the wave and what is that peak of the wave it is the maximum height that it has it is the maximum height what is the maximum height of the curve amplitude makes sense nonsense great makes sense okay so the wave function may have positive or the negative value depending upon the value of the coordinates and the main aim of Schrodinger equation is to give a solution for probability approach what we are actually trying to find out is where exactly can we find the electron what Heisenberg said was that you cannot find the position and the momentum of the electron at the momentum of a fast moving uh particle at the same point right that's what Eisenberg Heisenberg said but here what he is trying to do is he wants to find out what is the probability we don't even want to actually find out the position we just want to know that where might I find the electron probability okay yes so when the equation is solved it is observed that for some regions of space the value of PSI is a negative but the probability must be always positive and it cannot be negative and that is why that is why we cannot have a negative value probability has to be positive right which is why now we stopped using PSI and instead of that we started using PSI Square we started using PSI Square now what is PSI Square PSI square is the probability Factor huh PSI does not really have so much significance PSI does not have a physical significance at all in fact but PSI Square is important for us it actually describes the probability of finding an electron within a small space okay and the space in which there is maximum probability of finding an electron is called as the orbit yes it's called acids orbital getting my point yes now in quantum mechanical model in quantum mechanical model let's say that if you uh you know how I told you that you have PSI right if you solve it for PSI r as a function of r right you will actually get two parts you will get radial and angular radial plus angular now do you remember that just sometime back only we saw that s orbital is fear in it yes if s orbital is spherical can you tell me if angular part will be there or not no so can I write it that 4S for S orbital for S orbital what will happen PSI r PSI R radial part will be there but angular part will not be there okay so I'm just writing it angular cross radial correct got it yes all right now this PSI this PSI it cannot give you the spin quantum number but it can actually tell you all the others it can tell you the principal quantum number azimuthal quantum number and the and the Magnetic quantum number but it cannot give you the spin quantum number you're getting my point it cannot give you the spin quantum number it's not possible only okay it's not possible at all okay all right guys so till here we have understood till here we have understood just a minute just a minute where again where is the cursor yeah I guess it's not going to work anyway now the last bit is that we have to find out the graphs and everything which we will do very fast okay we will do it very fast oops did everything Shake because the mic actually just got stuck on my shoe and I pulled it very fast I hope I'm still audible I am right okay all right yeah so now what happens is now what happens is PSI Square we have understood right yes we have understood PSI Square yeah so there are times there are times when what happens is there are times when the PSI Square becomes zero yes there are times when PSI Square becomes 0. if it becomes 0 then do you know what that position is that part that particular place is actually called as a node you're like node what is node node is actually that space around the nucleus where the probability of finding an electron is almost zero okay where the probability of finding an electron is almost zero or just zero okay all right so what is node node is basically what is not I'm writing it down here the space around nucleus where oops it's it's you know what the time is uh 12 o'clock right now at night when I'm recording and uh I think things in the studio are just falling apart I have no idea if it's working but I just hope it is anyway so as I was telling the space around the nucleus where probability of finding electron okay where that's called as a node now you want to see a you you want to see a picture of a node I'll show you and you will actually understand okay so node is always given as n minus 1 yes how is it n minus one take a look at it so you basically you basically add the radial node and the angular node okay what do you do you basically add the angular node and the radial node okay and how do we do that how do we do that check it out yes so see n minus L minus 1 that's your radial node plus L if I do what will it be LL cancel n minus 1 and that's your unknown funny mathematics isn't it so now node can be of 2 times there is radial node and angular node what is radial node radial node RC these particular places where you cannot find the electrons say if it is a three s orbital in 3s there are 1 and 2 there are two nodes if it is One S there are no nodes if it is 2s there is only one node got it yes these are your nodes all right now when it comes to angular nodes so at this point so if I draw this double dumbbell or dumbbell at this part my chances of finding an electron is almost zero the electrons are probably here here here here here here here here here here here but not here so that becomes my angular node okay that becomes my angular node got it now in case of e orbitals you see the angular nodes are a little more right there are more number of angular nodes okay all right yes and now finally coming to the graph of it guys graph of it let's check it out let's check it out okay so final final time final lap of it let's just complete it together everybody yes so variation of radial wave function r with r okay what is it that is basically this capital r is nothing but PSI okay what is this capital r is nothing but PSI okay so PSI with respect to R this first this first graph please just remember it just draw a rectangular hyperbola what is this kind of graph this is called as rectangle Harper Bola rectangle hyperbola okay now what you have to remember is because if it is 2s if it is 2s check it out very interesting story okay very interesting story if it is 2s use the same thing n minus L minus 1 what is l l will be equal to 0 from the quantum number let's see for l yes L will be equal to 0 n is 2 yes n is 2 N is given to us L is 0 for n minus L minus 0 so 2 minus 0 minus 1 so it will be 1. now that here you have 1 understand that same kind of graph you will draw but what you will do is see you will take one dip see it is cutting the there will be a one node here do you see in case of 2s in case of 2s we had one node right see you have one node here right one node here right that's exactly what you are showing see one node one cut got it one cut now for 3s okay this is for 3s check it out n minus L minus 1. so what you can do is n is 3 l is still 0 minus 1 it will be 2 3 minus 1 is equal to 2 so now see one 2 2 cuts and just like that you can draw it for 4S for 5S for 6s but you can do it or do it for as many times as you want for S this is the graph okay now if I do PSI Square do you remember PSI square is always going to be positive negative negative positive negative multiplied with negative positive positive multiplied with positive negative right yes we are taking PSI Square correct so if I take PSI Square now what you have to do is this graph that you drew right okay let me show you see this graph that you drew it was like day is right it was like this this part is in the negative this part is in the negative part of the graph correct now because I'm taking PSI Square what I will do is I will draw it like this and this and exactly that is what we have done see the first one remains as it is second one see that's what I did that's what I did see one I touched it and then went like this exactly what happened yes now see for this graph what I have to do is just put it like this okay understand understand understand CCC like this it is going it is going like this and then it is going like this right I have to bring this to the positive part so what I will do is check it out instead of uh what I will do is see my graph came like this yes now it went like this it went like this then it went like this and then it went like this yes now instead of doing this I have to bring the negative part to the positive so what I will do is erase this and then see what I will do and that's exactly how my graph looks for 3s right yes got it now for four offer 3p okay now for 3p also you can remember it for 3p it's like days okay for three pay it's like this okay okay okay okay okay okay okay got it so now you are you can do it for everyone let's just check it out once for 2p s is done s is completely covered if it is 2p you have to remember this please remember this please remember this these two if you remember done sorted you can do the graph for anything and everything yes for 2p it goes like this and then done now for 3p if I do say n minus L minus 1 n will be 3 what is p for p what will it be L will be equal to what will it be it will be come on yeah L will be 1 minus one so it will be 3 minus 1 minus one two so one so see uh one cut and gone okay now for 4p if I do c n minus L minus 1 so 4 minus 1 minus 1 is equal to two see two cards will be there two cuts will be there check it out check it out see um uh like this one card here one cut here and done got it yeah and the very same way you can also draw it for 3D 3D and 2p they kind of looks very similar okay 3D and 2p they look very similar gotcha okay and then again the same way what you will have to do is you will also you can also do it for the four Pi Square R square vs you know the same way this is what we this is what we have done for radial wave now if you do again PSI Square same thing you have to do see 2p remains same yes but for 3p if you do see three p where is it huh three PC there was one cut at the bottom all you have to do is just bring it here and then go see three p will be same see thank you see easy peasy Biryani tasty yes now let's solve a question and the final is over the final love this chapter is over guys one or two questions and then we are done okay so the energy of an electron of two p y orbital is greater than 2px no energy will be same right less than 2 p z orbital low equal to 2s no same as that of 2px and 2p Z absolutely right 2p X Y and Z they are all at the same level right great now the wave function of an or this kind of this kind of questions do come in J but hello so please take a look at it the wave function of an orbital is plotted against the distance from the nucleus the graph represents see there are two cuts here guys two cuts if it is two cuts that means that it can be 3s right so n minus L minus 1 that means 3 minus 0 minus 1 if I do it can be two so two cuts yes it has to be 3s option C that's how you solve the graph now if radiation corresponding to second line of Bama series or Bama series of li2 plus ion if it is second line of bomber series that means guys so bummer what happens is bomber what happens is see if this is my n is equal to 2 if this is my n is equal to 2 this is my n is equal to 3 this is n is equal to 4 so this is the first line of the bomber Series this is the second line of the Palmer series that means we are talking about n is equal to 4 okay so second line of Bama series of li2 plus ion knocked out electron from first excited state of H atom then kinetic energy of ejected electron would be you know what this question please take it as a homework solve it on your own you will get the PDF no doubt about it you will get the PDF and with this note I'm gonna end the session today thank you so much for attending the session I hope that you have been able to understand everything don't forget to like comment and let us know that how it has helped you let us know about the homework problem if you can solve it let us know if there was anything that you wanted us to do more if I have missed out on any topic I don't think so but yeah please do let me know and if you think that this video has helped you don't forget to share it with your friends with this note lots of love and terrible bye see ya

Channel: Vedantu JEE English

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Keywords: structure of atom class 11, structure of atom, structure of atom one shot, atomic structure, structure of atom class 11 ncert, atomic structure class 11 ncert, atomic structure iit jee, shapes of orbitals, schrodinger equation, structure of atom in english, structure of atom in english class 11, structure of atom explanation in english, quantum numbers, atomic structure class 11, bohrs model, chemistry structure of atom class 11, vedantu, class11chemistry, cbseboards

Id: eiP5fOLXYmM

Length: 201min 20sec (12080 seconds)

Published: Wed Jul 05 2023