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Video transcript

we've already seen that the allowed values for the spin quantum number are positive 1/2 a negative 1/2 so an electron could have spin up or electron could have spin down and remember spin is in quotation marks because we can't really visualize an electrons spinning on its axis that's not really what it's doing and so we just call it the spin quantum number and so let's say we have let's say we have two electrons and each of our electrons has has spin up so let me do and draw that situation here so we have two electrons with spin up well an electron is is a moving charge I'm moving charges produce magnetic fields and so an electron is really just a tiny magnet and when you have two electrons with parallel spins the magnetic fields of those electrons add together so we call the situation paramagnetic so this situation here is paramagnetic the magnetic fields of the electrons add together if you have a situation where you have one electron with spin up and one electron with spin down the magnetic fields of those electrons cancel each other out and so we call this situation diamagnetic and let's get some some better better definitions for paramagnetic and diamagnetic so let's move down to here and let's look at the definition for paramagnetic so something that's paramagnetic has one or more unpaired electrons so we talked about an example where we had two unpaired electrons but of course you could just have one unpaired electron all right so that's like a tiny magnet with its own magnetic field and so up something that's paramagnetic is pulled into an external magnetic field that's tracted to an external magnetic field and we can figure out if a sample is paramagnetic or not by using the special balance that I have I have this picture this balance drawn down here so let's say that our paramagnetic sample is in here so right there in magenta and we haven't turned on the magnet yet so here we have a magnet there's a North Pole and a South Pole so before we turn the magnet on let's just say that our paramagnetic sample is balanced by by some some balancing weight over here on the right side right so there's a pivot point right here but we have we have everything perfectly all right so let's now turn the magnet on so we turn the magnet on and the magnetic field lines go from North Pole to South Pole like that and if we have a paramagnetic sample all right with one or more unpaired electrons our paramagnetic samples pulled into this external magnetic field that we've just turned on and so this is pulled down right so this whole part is pulled down and so let me go ahead and redraw it here so this would be pulled down into the magnetic field and so our our paramagnetic sample right is pulled into the magnetic field all right what does that do to our balance well of course that's going to pull this side down all right and so that's going to pull and our balance is going to is going to rotate about this axis right and so this part is going to go up alright so just simple physics and so this weights going to go up and so it's like our paramagnetic sample has gained weight and of course it hasn't gained weight just experiencing a force there's a magnetic force because it is a paramagnetic substance and so this this balance allows us to figure out if something is paramagnetic or not let's look at the definition for diamagnetic so for diamagnetic all electrons are paired alright so we have if we have spin up we have spin down and so the magnetic fields cancel and so a diamagnetic sample would not be attracted to an external magnetic field actually it produces its own magnetic field in the opposite direction so it's actually weakly repelled by an external magnetic field so we have these two definitions paramagnetic and diamagnetic and we can figure out if atoms or ions are paramagnetic or diamagnetic by writing electron configurations so let's look at a shortened version of the periodic table let's look at some elements and let's figure out whether those elements are para or diamagnetic let's start with helium so helium right here we need to write the electron configuration for helium so this would be 1 s1 and then we get 1 s2 so I'm assuming you already know how to write your electron configuration so we have 1 s2 which means we have two electrons in a 1s orbital so here's our 1s orbital we have two electrons and they must be spin paired alright so the electrons are completely paired and that means that helium is diamagnetic so helium is daya magnetic so helium atoms I should say let's do carbon next so let's find carbon let me change colors here so here's carbon on the periodic table if I wanted to write an electron configuration for carbon well it would be 1s2 alright so I'll start 1 s 2 and then we have 2 s 2 so 2 s 2 and then we have we're in the 2 P 1 and then 2 P 2 so 1 s 2 2 s 2 2 P 2 is the electron configuration for carbon if we write an orbital notation alright so we would have our 1s orbital here and our 2's orbital here and then we have three 2p orbitals like that so put in your electrons we have six electrons all right so two in the 1s orbital so we put those in two in the 2's orbital we put those in and remember UN's rule right we have two electrons in the P orbitals but we don't pair those spins right we don't pair those spins and so we have we have unpaired electrons right so we have unpaired electrons here for carbon when we draw out the orbital notation and unpaired electrons means that carbon is paramagnetic so carbon is para magnetic carbon atoms anyway all right let's do sodium and next so let's find sodium down here so here's sodium we need to write the electron configuration alright so that would be how would be 1s2 so let's write 1 s 2 and here 2 s 2 then we have 2p 6 so 2 P 1 2 B 2 2 B 3 2 P 4 2 P 5 2 P 6 so 2 P 6 it takes us to to the 3 s orbital alright so one electron in the 3s orbital so 3 s 1 so 1s2 2s2 2p6 3s1 is the electron configuration for sodium if we if we did that on our on an orbital notation right we would have one s orbital alright so we have two electrons in the 1s orbital 2's orbital we have two electrons in the 2's orbital 2p orbitals alright we have 1 2 3 4 5 6 and then we have 3 s 1 right so we have the 3 s orbital right here 1 electron in the 3s orbital well notice right one unpaired electron an unpaired electron means paramagnetic so sodium sodium is paramagnetic sodium atom anyway all right finally let's do let's do sodium ion so n a plus so the sodium atom has equal numbers of protons and electrons but the sodium ion we've lost one of those electrons alright so we're going to lose this outer electron here right so the sodium ion has this for an electron configuration 1s2 2s2 2p6 and so we lose this one electron notice for the ion now we have all paired electrons right so everything here is paired and if you have all paired electrons we're talking about diamagnetic so while the sodium atom is paramagnetic the the sodium I misspelled out there the sodium ion is diamagnetic and so it's just about writing your electron configurations and thinking about the definitions for paramagnetic paramagnetic and diamagnetic