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Organic Chemistry

Learn the toughest concepts covered in Organic Chemistry with step-by-step video tutorials and practice problems by world-class tutors.

1. A Review of General Chemistry

Molecular Geometry

Hybridization describes orbitals, but molecular geometry describes the shape of the atom. 


Molecular Geometry Explained.

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So now let's bring this all together talking about molecular geometry and Vesper theory. So Vesper theory is something that you should have learned in Gen. Cam. And what it basically says is bond sites will repel each other as much as possible. All right? And we already hinted at this when we talked about the bond angles of different atoms. Okay, I just want to draw a distinction. When I talk about hybridization. I'm always talking about the orbital's that air hybridizing that are blending so sp two s, p three whatever. When I talk about geometry, what I'm gonna be talking about is the actual shape of the molecule. Okay, what does it look like? If I were to put it under a microscope, what kind of shape would it have? All right, so let's go ahead and start off with these first three molecules. I'll just make them 12 and three. And what I want you guys to do is use the hybridization summary chart and use the rules that I taught you about bond sites to figure out what kind of hybridization in these three will have. So go ahead and pause the video trying to figure out the hybridization for all three. All right, so if you were using the rules correctly, what you would have noticed is that these air all sp three, even though they look very different, they're all SP three hybridized. And the reason why is because they all have four bond sites. Some of them have four atoms. Some of them have Adams and lone pairs, but that's still four bond sites total. All right, so now what I wanna do is enter in the amount of lone pairs that each one has. So, as you can see, this first one doesn't have any lone pairs. Okay, so I'm just gonna put zero. The second one has one lone pair, and the third one has to lone pairs. Oh, my gosh, too. All right. So I have one and two, and you can see that all these sp three hybrid is, but they all look different. Okay? And that's where the geometry comes in. Even though they're all sp three hybridized, we want words that are going to distinguish something that looks like 11 is very different. Looking from three, we want words that are going to describe those shapes. So kind of like I say that something looks like a circle or a square. I want shape names that are going to relate to these. Okay, so the name that I'm gonna use for zero lone pairs Does anyone know? I think I heard you say it. Tetra Hydro. Okay, you've heard of this forever. What? Least since Jenkins, the Tetra Hydro is the name given to the shape off four bond sites with zero lone pairs. So every every bond site is an atom or is a bond. All right. Now, if I have one lone pair, what I'm going to envision is that I think for all of these names think about that. I can't see the lone pairs. Remember that electrons are tiny, so imagine that I'm looking with a microscope and I can't see the loan Parad all What is this gonna look like? Well, if you think about it, it kind of looks like a pyramid, right? Okay, think about it. This is like the top of the pyramid. This is like Giza or whatever. So the name of this is the full name. Is tribunal parameter all or what sometimes is just called parameter. Okay, Tribunal parameter, but most of times just called parameter. All right, guys. So that's just the name of the shape, OK, And then finally what if we have to lone pairs? That means there's even less that I can see. So what? I'm just looking at this. All I see is something that is bent. Okay, So bent would be the name that I give to it when there's two lone pairs. Is that cool? So far? Awesome. So now what I want to do is move on to other types of hybridization. Okay, So what if I have this Adam right here in this Adam right here? Okay. I want us to also pause the video and figure out what kind of hybridization is thes two would have. So let's call these four and five. Figure out what their hybridization would be. All right? So both of these, because they have three bond sites each are gonna be SP two. Let me point out how it's three for the double bond. Oh, I have basically one Adam here. When Adam here. When? Adam here. That's three for the end. I have one. Adam here. When Adam here and a lone pair there, which is also three. Get it? So they're both SP two. Okay, but then they also look different. They don't look the same as each other. Notice that one of these has three things. Three atoms coming off of it. The other one only has to so far to talk about lone pairs. The lone pairs would be zero here and one here. Okay? And it turns out that these oftentimes will get different names as well. So the name of this first one just you guys know if you have an SP two is zero is tribunal. By the way, this is the same way that you spoke tribunal for tribunal parameter. So in case you wanted to spell out tribunal parameter, all would be this word tribunal plainer. Okay, Tribunal plainer is the name of it. The reason why is because when you have an SP to hybridize Adam, all of the groups are going to be on the same plane. So, in fact, if you thought about it, the way that I like to think of sp two is kind of like a sand dollar where? Imagine that this is like you're walking on the beach and you see, like, the sand dollar and you pick it up. That's basically the way triggered a player looks where you have those three lines. Line here, line here, line here and they're all on the same plane. Okay, you can. It's just a very flat object. It has two sides. Alright, so that's tribunal plainer. Does that make sense so far? Cool. Now what about it? Has one lone pair. All right. Now, this actually is a little bit controversial, and I've been looking for a universal answer, this question, but really, it turns out that it just varies by professor. So I'm just gonna tell you this some professors are going to call this bent because really, if you take out that lone pair, it looks bent. Does that make sense? So far, So some professors going to say that that's a bent. But then other professors are actually just going to say both of these Air Tribunal plainer. I'm gonna put here tp all right? They're just going to say, hey, both of them are triggered a plan or don't really worry about the lone pairs. All right, so I'm just gonna teach you to you both ways and just tell you guys to be aware to be a mindful When your professor says that maybe you even wanna ask them. Is this would you consider this molecule triggered a planner, or would you consider it bent? All right, You could also see, like, the answers to practice problems. However they answer them that will tell you. Okay, so I just wanted to let you know that those are two different ways of looking at it. Technically, tribunal planner is always correct. If you say that that's triggered a player, that should be correct. But bent is just a little bit more specific, and some professors want you to be that specific. Cool. So then finally live this last one, which is really easy. Ah, carbon. I'm not even gonna make you guys posit Ah, carbon with two groups. That should be what That should be SP In this situation, I don't worry about lone pairs or not lone pairs. It's always just gonna get the same name. And that is linear. Okay. And this is why it's very important. Whenever you're drawing triple bonds, it's very, very important that you always draw triple bonds. Sorry. Triple bonds in a straight line. Okay. In fact, if you draw your triple bond bent like with a zigzag, you will get points off taking off your test, okay? On the reason is because it makes it look like you don't know what you're doing. It makes it look like you have no clue that that's supposed to be a linear hybridization or a linear shape. Okay, so many times when you see true bond written, you're going to see it like this 12 and then like a triple bond like that and that means that's right over my head. But that means that you're indicating that Hey, this has a bond angle of 180 degrees, and it's linear cool.

Note: Many professors refer to ALL sp2 hybridized atoms as “trigonal planar” even though that is technically not correct for atoms with lone pairs. Just go with the flow if that happens!

Let's find the hybridization and geometry of the indicated atoms in the following molecules:


Predict the hybridization and molecular geometry

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All right. So for this first one, what I noticed is that this oxygen, um, even though it looks like it only has to bond sites, we know that can't be the case because it has to fill it octet. So remember this actually has two lone pairs. Okay, if you didn't draw those in, then you're gonna be super confused. Alright, That has to own pairs. So that means this is gonna be SP three. And it's SP three that has two lone pairs. That means that the name of this is bent. Is that cool? Let's look at this next one. This next one looks like it only has to bond sites. I'm talking about this one right here. It looks like it only has to. But remember, there's a hydrogen there. You have to draw that hydrogen because if not, the octet wouldn't be completed. Now, if this is throwing you off adding stuff like Johnny, how would I know there's a hydrogen? How would I know if there's a lone pair, go back and review what I was talking about with the octet rule and with bond line structures? Because that means that you're having a hard time interpreting. Ah, bond line structure. That means you have to go back and practice. All right, So the bond line structure means there's an h there. So I know that I have three bond sites and there's no lone pairs, So this is just gonna be S p two and it's gonna be tribunal plainer. Cool. Then you have our last one over here. Once again, it looks like it has to bond sites, but we know that can't be the case, because then carbon would be very angry at us. It needs to hydrogen. Okay. How did we know that from using bond line structures? So we have four different groups here. They're all atoms. No, there's no lone pairs, so there's gonna b S p three and it's gonna be Tetra hydro. Easy, right? Once you learn it, it's like second nature. But at the beginning, it could be a little confusing. So now I hope that made sense to you guys, and I want to do some practice problems.

Determine the hybridization of the following selected atoms: 


PRACTICE:Determine the hybridization and molecular geometry of the following selected atoms: