Q2. Science 9. Module 1. The Quantum Mechanical Model (Part 1)

hello my dear students welcome back to my YouTube channel this is me once again teacher teen your science teacher for today's video so quantum mechanical model which is the first Topic in your grade nine science nine and chemistry [Music] and of course if you're new to this channel don't forget to subscribe like and hit the notification Bell for more updates in science nine foreign [Music] known as the quantum mechanical model has emerged [Music] in quantum mechanical model A China explains discrete line Spectrum observed when light was emitted by different elements and of course Sydney is [Music] and there are different you know there are numerous numbers or there are numerous models of the atom that has been postulated based on the experimental results including the discovery of electrons [Music] nucleus which is not discovered Yana discovered Earnest Rutherford okay so structure planetary models solar system it's a solar system which is Young electrons is around positively charged nucleus like the rings around Saturn or alternatively the planets around the Sun in this lesson you will learn that the quantum mechanical model of the atom describes the energies and of course the position of the electrons so in particular we will also develop a picture of electron Arrangements in atops a picture that allows us to account for the chemistry of various elements planetary model okay okay model of an atom so if you can still remember in 1911 at the age of 25 imagine that 25 years old long but Neil boars already received his PhD so PhD it means uh doctor of philosophy in physics so he was convinced that the atom could be a picture as a small positive nucleus with electrons orbiting it okay or orbiting around it structure of an atom uh solar system electrons [Music] okay now over the next two years so sibor uh hydrogen atom with quantized energy levels so in this case [Music] electron moving in a circular orbits corresponding to the uh various allowed energy levels uh by absorbing or emitting Photon of light with exactly the correct energy content discussion well at first a Boar's model appeared very promising so very perfect it uh it fit the hydrogen atom very well however okay [Music] hydrogen other than Hydra I mean other than hydrogen because further experiment shows the divorce model is fundamentally incorrect so although the way for other theories it is important to realize that the current theory of atomic structure is not the same as the Bohr model okay now so let us proceed with the discussion about the wave mechanical model of an atom 1920s of course apparently young uh Discovery Millennials bore uh or your worst model was incorrect the reason why uh there are scientists who still pursue to discover new approach in atom so there are two young physicists see Louise Victor De broccoli from France and Irwin Schrodinger from Austria they suggested that because light seems to have both weight and particle characteristics wherein it behaves simultaneously as wave and a stream of particle so um the electron might also exhibit both of these characteristics electron was a tiny particle so this scientist said that it might be useful to find out as a wave when Schrodinger carried out a mathematical analysis based on this idea model for the hydrogen atom is also suited uh to other models or to other atoms which is do not failure using this his mathematical analysis based on this idea so defeated we will now know and we will now explore a general picture of this model and this is what we call the wave mechanical model in circular orbits but in wave mechanical model on the other hand so in the internet mechanical mathematical description of electrons motion called wave function or atomic orbital orbitals are nothing like orbits squaring the orbital gives the volume of space in which the probability of finding the electron is high the electron cloud or the electron density the model in this figure gives no information about when the electron occupies a certain point in space or how it moves in fact we have good reasons to believe that we can never know the details of electron motion but one thing we feel confident about is that the election does not overbeat the nucleus in circles as bore suggested [Music] [Music] corresponding to the orbital size shape orientation in space now later it was found out that one needed a quantum number associated with the electron spin yeah okay now let us discuss the different quantum numbers and orbitals quantum number so the first quantum number which is the principal quantum number which is symbolized letter N so it describes the size and energy of the orbital and relative distance from the nucleus okay so again so principal quantum number letter N adding symbol diyan so um possible values principal quantum numbers I one two three four and so on so there are positive integers so the smaller the integer or the smaller the value of n so who won is [Music] designating the shell the electron is occupying so and of course each shell contains one or more subshells and each with one or more orbitals orbitals s or vital the p orbital the D orbital and of course the F orbital so s p d Fiona in each shell contains one or more subshells with uh each with one or more orbitals so the second quantum number can in amperes I uh principal quantum number so the second one is the angular momentum quantum number or letter L so it describes the shape of the orbitals angular momentum quantum number so since we described it orbitals is related it's a principle quantum number and in value zero so zero to n minus one so for example if m is four okay so then the possible values of L could be zero one two and three okay and when it comes to the orbital so momentum quantum number L is zero so it is [Music] the greater the value of n of course is the larger is the sphere foreign okay sharp and it has spherical shape okay [Music] is zero it is one [Music] okay and is one so is pi orbital okay is stands for principal okay [Music] um two lobes of high electron density now and then of course as you can see two lobes of high electron density on either side of the nucleus for an hour glass or dumbbell shapes is to orbital okay variety of shapes it stands for diffuse okay and the orbital has four laws okay so again if the angular momentum quantum number is 2 it is the orbital this stands for diffuse and anxious okay has four lobes with a variety of shapes [Music] a f orbital with more complex shapes and as you can see C and F is f is fundamental [Music] F orbital so complex science and okay so Ayan yeah box quantum number if L is zero that is s orbital and this has spherical shape if L is one it does p orbital and it has two lobes if L is 2 that's the orbital and as you can see it has a variety of shapes and if L is three that's F orbital which is with more complex shapes so s stands for uh sharp P for principle D for diffuse and F4 fundamental okay next the third quantum number is what we call the magnetic quantum number or M L so and with this uh subscription l so it describes the orientation of the orbital sound around the nucleus okay so some magnetic quantum number so angular momentum quantum number is three so a magnetic quantum number I negative three negative two negative one zero positive one positive two or positive three if the angular lower momentum quantum number is one so on possible magnetic quantum number one is pointing negative one zero or positive one L is two of course magnetic quantum number Nyan is negative two negative one zero positive one and positive two okay [Music] quantum numbers okay now let's proceed with the fourth quantum number which is the spin quantum number okay so for the last quantum number we have the spin quantum number so m s okay so it indicates the direction of the electron is spinning quantum number there are only two possible answer for that so the possible the two passive values I foreign must have an uh spin quantum number of positive one-half and the other one or the other electron must have negative one-half but these are spin paired electron [Music] spelling okay spin paired electrons electrons same orbitals so let us have this if n is 7 or if the principal quantum number is 7 what are the possible values of L okay so L that's the angular momentum quantum number so devices in relation to the principal quantum number it's it is always n minus one so n minus one so it is seven so seven minus one that's six so if n is seven so the possible values of L will be zero until six so L it can be zero one two three four five six okay zero one two three four five six okay next question so if n is three and L is two so n minus one that's two so a possible L is 0 1 2. angular momentum quantum number is two then what are the possible values of ml or the magnetic quantum number is positive uh numbers and negative numbers it can be negative two negative one zero positive one and positive two so [Music] angular momentum quantum number is two okay yeah very good okay thank you for listening part one I'm adding module one week one so in our next discussion we're going to discuss about the election configuration [Music] week one module one so stay tuned on this channel and uh let us discuss the next Topic in chemistry so this is me once again teacher team your science teacher for today's Vlog if you're new to this channel don't forget to subscribe like and hit the notification Bell for more updates in science nine I hope to see you soon bye [Applause] [Music] thank you [Music] foreign [Music] [Music] [Music] foreign [Music] [Music] foreign [Music] [Music] [Music] foreign [Music] [Music] foreign [Music]

Channel: Khristine Min Jin

Views: 12,939

Keywords: chemistry, science9, quantum mechanical model, electron configuration, science, module

Id: do02nnyMJBE

Length: 24min 38sec (1478 seconds)

Published: Wed Nov 30 2022