in this video we're going to talk about orbitals energy levels sub-levels quantum numbers and things like that now an orbital is simply the most probable location to find an electron so let's say this is nucleus we're going to consider the bohr model of the atom so i'm going to draw circular orbits so this is going to be the first energy level n equals 1 and here we have the second energy level n equals two and here's the third energy level an equal stream an electron that occupies the third energy level has more energy than one that occupies the second energy level n represents the principal quantum number it describes the size and the energy of that orbital so as n increases the distance from the nucleus increases as well so electrons that are closer to the nucleus exist at lower energy levels electrons that are further away from the nucleus exist at higher energy levels so that's the first quantum number that you need to be familiar with so n is the principal quantum number so keep in mind n is associated with the energy level l is the angular momentum quantum number and it describes the shape of the orbital so when l is zero what you have is the s orbital and so this orbital looks like a sphere when l is one you have the p orbital which looks like a dumbbell and when l is 2 you have the d orbital which is a cloverly for the most part and when l is 3 you have the f orbital which looks pretty strange which i'm not going to draw in this video so just keep that in mind l describes the shape of the orbital and n the principle quantum number describes the size and the energy level of that orbital by the way s also corresponds to the sublevel it describes the shape of the orbital but you can also think of it as the sublevel now let's talk about the relationship between n and l l is always less than or equal to n minus one so when n is one you can only have one value for l that's zero which corresponds to the s sublevel now when n is two l can be zero or one but not two so in the second energy level you can have the s sub level and the p sub level in the third energy level l can be zero one or two so the third level can have the s sub level the p sub level and the d sub level so if you look at the electron configuration of certain elements you'll see that there's one s there's no such thing as one p in the second energy level we have 2s and 2p but 2d is it doesn't exist in the third energy level we have 3s 3p 3d but 3f is impossible now for the fourth energy level you have four sub levels l can be zero one two or three so this is going to be s p d f so in the fourth energy level you have the 4s sub level the 4p sublevel the 4d sub level and the 4f sublevel so notice that the end value is always equal to the number of sub levels so when n is six you should expect six sublevels when n is three we have three sub levels s p and d now the next quantum number that you need to know is the magnetic quantum number m sub l so m sub l describes the orientation the orbital relative to other similar orbitals in that atom so how do we describe this well we know that the s sublevel has only one orbital the p sublevel if you draw the orbital diagram has three orbitals now for s we know that l is zero for p l is one ml will always vary between negative l and l so in this example l is zero so ml has to be zero now for p l is one so ml is going to vary between negative one and one including zero so notice that ml describes each orbital in the p sub level the p sub level has three orbitals you have p x p y and p z so p x is in basically along the x axis p y is along the y axis and then you have p z which is along the z axis and so these three orbitals within the p-sub-level has different orientations so one of these numbers corresponds to px one of them corresponds to py and the last one corresponds to pz it doesn't have to be net water but each orbital corresponds to one of these designations now let's talk about the d sublevel for the d sub level we said that l is two and d has five orbitals and m l we know it's between negative l and l if l is two then m o has to vary between negative two and two so we can place five ml values for each orbital and so ml describes the orientation of the orbital so each box that you see here has a certain ml value now the last quantum number that you need to be familiar with is the electron spin and there's only two possibilities an electron can only spin in a clockwise direction or in a counterclockwise direction and so that's why there's two possibilities it can be positive a half or it could be negative a half and within an orbital you can place the electron with an up arrow or with a down arrow so when the spin is up ms is plus one half when the spin is down it's negative one half so according to paulie's exclusion principle every electron within an atom has a unique set of four quantum numbers so you can think of those four quantum numbers as the address of each electron within an atom so let's say if we want to talk about the 2p5 electron what are the four quantum numbers that describes the 2p5 electron so what's n l ml and m sub s that correlates to this electron and the principal quantum number corresponds to the number that you see in front so n is two that means this electron is in the second energy level l is based on the sub level p now if you recall s has an l value of zero p has an l value of one d has an l value of two and f has an l value of three so l is one now we need to find the ml value so what you want to do is draw the orbitals that's found in the p sublevel keep in mind p has three orbitals now because l is one ml is going to vary between negative one and one now we need to focus on the fifth electron in the p sublevel so here's the first one the second the third the fourth and the fifth so the fifth electron is found in this orbital which has an ml value of zero now the electron spin based on what we have here we have a down arrow so the spin is minus one half so that's a quick and simple way in which you could find the four quantum numbers that corresponds to a specific electron so let's try one more example go ahead and find the four quantum numbers that corresponds to the 3d5 electron you can pause the video if you want to now the easiest one to see is the number in front of the d sub level so n is 3 this number corresponds to the energy level now what is the l value for the d sub level keep in mind l is 0 for s l is one for p and for the d sub level l is equal to two now within the d sub level we have five orbitals and if l is two ml is going to vary between negative l and l so it's going to vary between negative two and positive two so now we're looking for the fifth electron so this is going to be the first one the second the third the fourth so here's the fifth one so the fifth electron is in this orbital where ml has a value of two now notice that we're dealing with an up arrow so the electron spin is positive one half so that's it for this video if you want to get more examples on this stuff i've created other videos on youtube entitled quantum numbers how to calculate the maximum number of electrons and other stuff like that so you can look it up on youtube or you can go to my channel and check out my chemistry video playlist and find more videos on this stuff as well so thanks again for watching and have a good day you