Energy Levels, Energy Sublevels, Orbitals, & Pauli Exclusion Principle

chemistry lecture number 21 energy levels energy sub levels orbitals and the Pauli exclusion principle in the Bohr model of the atom electrons circle the nucleus in the same way that planets orbit around the Sun negative electrons are attracted to the positive nucleus and consequently it takes energy to move an electron away from the nucleus to an outer circle alright so Rutherford came up with his model of the atom where the protons occupied the center of the nucleus and he said the electrons were very far away and then Bohr further developed this model of the atom by saying that the electrons orbit the nucleus now the electrons with a negative charge are going to be attracted to the positive charge of the nucleus remember opposite charges attract and if I want to pull an electron away from the nucleus it's going to take energy so these circles are sometimes referred to as energy levels and the further I want to pull it away from the nucleus the more energy it takes so the more outermost the circle the higher energy the electron has so let's sort of reiterate that so the circles where the electrons orbit or refer to as energy levels or shells electrons in the outermost circles have higher energy since it requires more effort to pull the electronic greater distance from the nucleus now the energy levels are numbered 1 2 & 3 etc energy levels are called principle quantum numbers the letter n is used to represent the energy level the smaller the number the closer the energy level is to the nucleus the energy level that is closest to the nucleus has a value of n equals 1 all right so let's see a picture of what these words mean all right so each of these black bands represent energy levels the electrons are inside the energy levels orbiting the nucleus this circle right here is the closest circle so it has an energy level equal to one and then the second outermost is N equals two and so on this red dot here is the nucleus K L m and n are sometimes used instead of the numbers 1 2 3 & 4 that's they used more in college or maybe yeah higher-level chemistry but for high school level usually we just refer to energy levels as 1 2 3 & 4 instead of K L m and N and as you go further and further away from the nucleus the energy of the energy level increases so the electron is said to have higher energy now each energy level can only hold a certain number of electrons the first electron can hold our first energy level only hold 2 electrons the second energy level can hold only 8 and the third energy level can only hold 18 electrons let me show you a picture of that okay so here's our picture of the atom here's the nucleus right here each of these rings represent energy levels where the electrons are orbiting so in this first circle right here notice there are only two electrons and then in this second circle you have 2 4 6 8 electrons and then in this outermost one there are a total of 18 electrons in the third energy level so I'm going to make a chart listing the energy level against the number of electrons and let's see if we can see a general trend you see a pattern the first energy level we can put to second eight third 18 4 32 so as the energy level increases we can put more more electrons in and in fact we can even use a formula to predict the number of electrons that can fit into a shell the formula is 2n squared so for example let's say the maximum number of electrons that can fit into the fourth energy level we want to calculate that how many electrons can we put into the fourth energy level well we use our formula and is going to be the energy level we're interested in the fourth energy level so it's going to be 2 N squared or two to the fourth squared 4 squared is 16 2 times 16 is 32 we can put 32 electrons into the fourth energy level now within energy levels our sub levels and the sub levels are labeled s P D and F you need to memorize these four sub levels so here's a chart listing the sub levels that are inside the energy levels first has an S sub level second energy level has an S and P sub level third energy level as SP and D fourth energy level has s P D and F you notice that the number of sub levels in an energy levels equal to the number of the energy level first energy level has 1 sub level 2 as second energy level is 2 sub levels third energy level has 3 sub levels and so on it's kinda like the floors with a maybe an inverted pyramid now the first floor you have you know one room and second floor you have two apartments and the third floor you have three apartments and so on so I want to draw a picture of this and the way we're going to draw the picture is we're going to take our initial picture of the atom with the nucleus and just with the energy levels and what we're going to do is I'm just going to draw this section of our model of the atom and we're going to look and see what's inside each of these black bands we're going to see what's inside each of these energy levels I'm not going to draw the whole thing I'm just going to draw this little section right here okay so the first energy level right here looking at it close up is this energy level right here okay so here's the nucleus here's the first energy level here's the second energy level here's the third energy level and here's the fourth energy level so the first energy level has one sublevel s the second energy level has two sub levels s and P the third energy level has three sub levels SP and D and the fourth energy level has s P D and F just like that little chart we drew you know and then so you need to memorize this so the first energy level has one s the second energy level has s and P third energy level has s P and D and fourth energy level has s P D in F just like the previous paper I showed you alright so energy levels one two three and four have sub levels inside of them s SP SP D s P D and F now inside the sub level there are orbitals alright so we've gone from energy levels to sub levels and now inside the sub level our orbitals so this is the final location where electrons reside and each sublevel has a certain number of orbitals alright so the sublevel s has one orbital sublevel P is three sublevel D has five and sublevel F has seven and we can put a maximum of two electrons inside each orbital so now what we're going to do is we're going to show you what's inside each of these bands so we're sort of zooming in before we show what was inside the energy levels so these are what's inside the energy levels and now we're going to look and see what's inside the sublevels okay so inside the sublevel you're going to see orbitals and this is what's inside the sublevels alright once again here's the first energy level here's the sublevel inside of it here's the second energy level here the sublevels inside here's the third energy level here the sublevels inside and then here's the fourth energy level here are the sub levels inside and then each of these sub levels has orbitals in it previously we had shown you that the number of orbitals these little oval things is based on this chart so remember s has one sublevel I'm sorry one orbital and then he has three orbitals we'll take a look at this s has one ps3 alright and then D has five five little ovals and then f has seven ovals and this is the final location of where the electrons go so we can put the electrons in the orbital so I'm going to put dots right here so these dots represent the electrons and notice that I'm only putting two dots in each oval why because a maximum of two electrons can occupy an orbital that's why so you can only put a maximum of two dots or two electrons in each orbital now we're going to talk about something called the Pauli exclusion principle when electrons occupy orbitals they spin on their axis so electrons spin if two electrons occupy an orbital they must spin in opposite directions this is the Pauli exclusion principle so when the electrons occupy the orbitals if these little dots represent electrons one electron we have to spin in one direction and the other electron would have to spin in the other direction that's just a rule now instead of drawing dots to represent electrons will be using arrows to symbolize as spinning electrons so an arrow pointing up is an electron that's spinning in one direction and an arrow pointing down is an electron spinning in another direction so on a future lecture the way we would show where the electrons are going is if I draw an arrow pointing straight up that represents an electron spinning in one direction and if I draw an arrow pointing down that represents an electron spinning in another direction so we use arrows instead of dots to represent electrons and the up-and-down orientation just indicates that they're spinning in different directions alright so let's sort of summarize electrons orbit the nucleus and circles called energy levels so that would be like this is the nucleus here are the energy levels and then inside the energy levels or sub levels s P D and F inside the sub levels or orbitals so it goes from energy level and then inside the energy level or sub levels and then inside the sub levels our orbitals you need to memorize these charts if you don't have these memorize you're not going to understand the next lecture so memorize the number of the sub levels that are inside each of the energy levels this is from previous part of today's lecture and then also memorize this chart the number of orbitals in each sub level so you should memorize it SS 1p s 3 D S 5 and F has seven for a PDF transcript of this lecture go to wwe.com this has been chemistry lecture number 21 energy levels energy sub levels orbitals and the Pauli exclusion principle

Channel: Richard Louie Chemistry Lectures

Views: 1,157,579

Keywords: Energy Levels, Energy Sublevels, Orbitals, Principle Quantum Number, Chemistry, Pauli Exclusion Principle

Id: J-DjEIlynjE

Length: 12min 10sec (730 seconds)

Published: Wed Feb 10 2016