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Current time:0:00Total duration:16:23

sp³ hybridized orbitals and sigma bonds

Video transcript

let's remind ourselves a little bit of what we already know about orbitals and I've gone over this early on in the regular chemistry playlist but let's say that this is the nucleus of our atom super small and around that we have our first orbital the 1s orbital and the 1s orbital you can kind of just view it as a cloud as a cloud around the nucleus so you have your 1s orbital and it can fit two electrons so the first electron will go into the 1s orbital and then the second electron though will also go in the 1s orbital so for example hydrogen has only one electron so would go into 1s helium has one more so that will also go into 1s orbital after that is filled then you move on to the 2's orbital you move on to the 2s onto the 2's orbital and the 2's orbital you can view it as a shell around the 1s orbital and all of these you know you can't really view it in our conventional way of thinking you can kind of view it as a probability cloud of where you might find the electrons but for visualization purposes just imagine it's kind of a shell cloud around around the 1s orbital so imagine it as kind of a as a fuzzy shell around the 1s orbital so it's around the 1s orbital and your next electron will go there will go there and then the fourth electron will also go there and I drew these arrows upward and downward because the first electron that goes in the 1s orbital has a as a has one spin and then the one the next electron to go into the 1s orbital will have the opposite spin and so they keep pairing up in that way they have opposite spins now if we keep adding electrons now we move to the 2p orbitals we move to the 2p and there's actually you can view it as there are 3 2p orbitals and each of them can hold two electrons so we can holder hold a total of six electrons in the 2p orbitals and let me draw them for you just couldn't visualize it so if we were to label our axes here so think in three dimensions so imagine that that right there is the x axis and that is our x axis let's let me do this in different colors let's say that this right here is our Y axis that is our y-axis and then we have a z-axis I'll do that in blue so let's say we have a z-axis just like that you actually have a p-orbital that goes along each of those axes so you could have your so let me do it so you have your two we do this in a let me do it in the same colors so you have your two to P sub X orbital and so what that will look like is a dumbbell shape that's going in the X direction so let me draw my my best attempt at drawing this it's a dumbbell shape that goes in the X direction in kind of both directions and it's actually symmetric I'm drawing this end bigger than that end so it looks like it's coming out at you a little bit but let me draw it a little bit better than that you can do a better job and maybe it comes out like that and or get remember these are really just probability clouds but it helpful to kind of visualize them is maybe a little bit more things that we would see in our world but I think probability clouds the best way to think about it so that is the 2px orbital and then I haven't talked about how they get filled yet but then you also have your 2 py orbital which will go in this axis but same idea kind of a dumbbell shape in the y-direction going in both along the y axis going in that direction and in that direction then of course so let me do this to P Y and then you also have your 2 PZ you also have your 2 PZ and that goes in the z direction up like that and then downwards like that so when you keep adding electrons the first so so far we've added 4 electrons if you add a fifth electron if you add a fifth electron you would expect it to go into the 2px the 2px orbital right there so even though this 2px orbital can fit two electrons the first one goes there the very next one won't go into that when it actually wants to separate itself within the p orbital so the very next electron that you add won't go into 2px it'll go into 2 py and then the one after that won't go into 2 py or 2px it'll go into z they try to separate themselves and then if you add another electron if you add let's see we've added one two three four five six seven if you had an eighth electron that will then go into the 2px orbital so the eighth electron would go there but it would have the opposite spin so this is just a little bit of review with a little bit of visualization now given what we just review let's think about what's happening with carbon carbon carbon has six electrons six electrons its electron configuration it is 1s 2 2 electrons in the 1s orbital then 2's 2 then 2p to right only has 2 left because it has a total of six electrons to go here then there then two are left to fill the P orbitals so if you go based on what we just drew and what we just talked about here what you would expect for carbon when you would expect for carbon let me just draw it out the way I did this so you have your 1s orbital your 2's orbital and then you have your 2px orbital your 2 P Y orbital and then you have your 2p z orbital if you just go straight from the electron configuration you would expect carbon so the 1s orbital fills first so that's our first electron our second electron our third electron and then we go to our 2's orbital that fills an X third electron then fourth electron and then you would expect maybe your fifth electron to go in the 2px we could have said two py or 2z just depends on how you label the axes but you would have your fifth electron go into one of the P orbitals and then you would expect your six to go into another so you would expect that to be kind of the configuration for carbon and if we were to draw it if we were to draw it let me draw our axes so that is our y-axis and then this is our x-axis that let me draw it a little bit better than that so that is the x axis and of course you have your z axis have to think in three dimensions a little bit a squiggly line there so let me then you have your z-axis just like that so first we fill the 1s orbital so if our nucleus is sitting here our one s orbital gets filled with two electrons you can imagine that as a little cloud around the nucleus then we fill the 2's orbital and that would be a cloud a cloud around that kind of a shell around that and then we would put one electron in the 2p X orbital so one electron will start kind of jumping around or moving around depending on how you want to think about it in that orbital over there 2px and then you'd have the next electron jumping around or moving around in the 2py orbital so it would be moving around like this and if you went just off of this you would say you know what these guys this guy over here and that guy over there is lonely he's looking for a opposite spin partner this would be the only places that bonds would form you would expect some type of bonding to form on the with the X orbitals or the Y orbitals now that's what you would expect if you just straight-up kind of stayed with this model of how things feel and how orbitals look the reality of carbon and I guess the simplest reality of carbon is if you look at a at a methane molecule is very different than what you would expect here with a methane first of all what you would expect here is that carbon would probably maybe it would form two bonds but we know carbon forms four bonds that it wants to fill it it's it wants to pretend like it has eight electrons that frankly almost every every atom wants to pretend like it has eight electrons so in order for that to happen you have to think about a different reality this isn't really what's happening when carbon bonds so not not what happens when carbon bonds what's really happening when carbon bonds and this will kind of go into the discussion of sp3 hybridization but what you're going to see is it's not that complicated of a topic it sounds very daunting but it's actually pretty straightforward what really happens when carbon bonds because it wants to form four bonds with things is its configuration you could imagine looks more like this it looks more like this so you have one s and we have two electrons there and then you have your 2s 2px 2py and 2pz now what you can imagine is it wants to form four bonds it has four electrons that are willing to pair up with electrons from other molecules in the case of methane that other molecule is a hydrogen so what you can imagine is is that the electrons actually maybe the hydrogen takes attracts this brings this this electron right here into a higher energy state and puts it into two Z that's one way to visualize it so this other guy here maybe ends up over there and then these two guys are over there and over there now all of a sudden it looks like you have four lonely guys and they are ready to bond and that's actually more accurate of how carbon bonds it likes to bond with four other people now it's a little bit arbitrary which electron it ends up in each of these things and even if you had this type of bonding you would expect you would expect things to bond along the XY and z axis the reality is the reality of carbon is that these these four electrons in its second shell don't look like they're in just you know the first one doesn't look like it's just in the S orbital and then the peas and y&z for the other three they all look like they're a little bit in the S and a little bit in the P orbitals so let me let me make that clear so instead of this being a 2's what it really looks like for carbon is that this looks like a - sp3 orbital this looks like a - sp3 orbital that looks like a - sp3 orbital that looks like a 2sp3 orbital they all look like they're kind of in the same orbital and this special type of you know sounds very fancy this sp3 hybridized orbital what it actually looks like is something that's in between an S and a P orbital it has a 25% s nature and a 75% P nature you can imagine it as being a mixture of these four things that's what that's the behavior that carbon has so when you mix them all when you mix them all instead of having a an S orbital so if this is a nucleus we do cross section an s-orbital looks like that and a p-orbital and a p-orbital looks something like that in cross section when you so this is a I mean this is an S and that is a P when they get mixed up the orbital looks like this an sp3 orbital looks something like this looks something like this this is an SP hybridized sp3 orbital hybrid just means a combination of two things hybrid is a hybrid car it's a combination of gas and electric high hybridized orbital it's a combination of s and P and a hybridized sp3 orbitals are the orbitals when carbon bonds with things like hydrogen or we really when it bonds with anything and so what if you looked at a molecule of methane and you know people talk about high sp3 hybridized orbitals all they're saying is that you have a carbon in the center maybe let me draw the way let's say that's the carbon nucleus right there and instead of having 1s and 3p orbitals it has four sp3 orbitals it has four sp3 orbitals so let me try my best at drawing the four sp3 orbitals so let's say that this is the big lobe it's kind of pointing near us and then has a small lobe in the back and then you have another one that has a big lobe like that and a small lobe in the back and then you have one that's going back behind the page so let me draw that so you can kind of imagine a three-legged stool and then it's small lobe will come out like that and then you have one where the big lobe is pointing straight up the big lobe is pointing straight up and it has a small lobe going down you can imagine it's kind of a three-legged a three-legged stool one of them's behind like that it's pointing straight up so three-legged stool with something yeah I guess you know it's it's kind of like a tripod I guess it's the best way to think about it and so that's cart that's the carbon nucleus in the center and then you have the hydrogen's so that's our carbon right there and then you have your hydrogen's you have a hydrogen here a hydrogen just has one electron in the 1s orbital so the hydrogen is has 1s orbital you have a hydrogen here just has a 1s orbital it has a hydrogen here 1s orbital hydrogen here 1s orbital and so this is how the hydrogen orbital and the carbon orbitals get mixed the carb the hydrogen's 1s orbital bonds with well each of the hydrogen's 1s orbital bonds with each of the carbons sp3 orbitals and just so you get a little bit more notation so when people talk about hybridized sp3 orbitals all they're saying is look carbon doesn't bond doesn't bond when once carbon let this right here is a molecule of methane right this is ch4 ch4 or methane and it doesn't bond like you would expect if you just went with straight vanilla s and P orbitals if you just want a straight vanilla s P orbitals the bonds would form maybe you know the hydrogen might be there and there and if it had 4 hydrogen's you know maybe there and there depending on how you want to think about it but the reality is it doesn't look like that it looks more like a tripod it has a tetrahedral shape it has a tetrahedral shape tetrahedral shape and the best way that that can be explained if you I guess the shape of the structure is if you have four equally four of the same types of orbital shapes and those four types of orbital shapes are hybrids between SS and PS and now one other piece of notation to know and sometimes people think it's very fancy term but when you have a bond between two molecules where the orbitals are kind of pointing at each other so you can imagine right here the this hydrogen orbital is pointing in that direction this sp3 orbital is pointing that direction and they they're overlapping right around right around here this is called a sigma bond this is called a sigma sigma bond we're kind of the overlap is in is in along the same axis is if you connected the two molecules over here you connect the two molecules the overlap is on that same axis this is the form the strongest form of covalent bonds and this will be a good basis for discussion maybe in the next video when we talk a little bit about PI bonds but the big takeaway of this video to understand what does it mean what is a sp3 hybridized orbital nothing fancy just a combination of s and P orbitals has 25% s character 75% P character which makes sense and it's what exists when carbon forms bonds especially in the case of methane that's what describes its tetrahedral structure he'd reluctor that's why we have a bond why we have an angle between the various branches of 109 point five degrees which some teachers might want you to know so it's useful to know if you take this angle right here 109 point five that's the same thing as that angle or if you were to go behind it that angle right there 109 point five degrees explained by sp3 hybridization the bonds themselves are Sigma bonds the overlap is along the axis connecting the hydrogen and the carbon