 Okay. So, let's go through effectively this slide and treat it as a problem, okay? So, there's different types of formulas that you can use to emphasize different things when, especially when you're talking about organic molecules, okay? So, of course, there's the molecular formula as you all know. This molecule is called butane that we're about to draw on, okay? Okay, this molecule is the stuff that if you go to the convenience store in BioLider, that's what's in that light, okay? Butane's molecular formula is C4H10, okay? So, from that, we just know that it has four carbon atoms and ten hydrogen atoms. We don't really know how they're arranged, okay? In fact, we'll talk about these things called isomers in a second, okay? But since I told you it was butane, we're going to go with that fact, okay? So, I know what the structure of butane looks like. So, you're just going to have to believe me for right now. Or if you've got a phone, you can look it up, okay? Anyway, so let's do the expanded structure. Well, let's start with the condensed structure of butane, okay? So, we can expand this to, like, give us a little bit more information about it, okay? So, the condensed structure is to show the carbon chain all stuck together, but just in one line, okay? So, in this case, we would say butane is CH3CH2CH2CH3. So, that's the condensed structure. You don't want to be on video, huh? Not even your voice, huh? Nobody's going to even know who you are. So, it's called the condensed structure, the condensed structural formula. You can even condense this even more if you wanted to, because you see that these two CH2's are the same, so it's a repeat of that. So, this effectively is the same thing as CH3CH2CH3. You want to be real convinced. So, let's expand this structure. We'll draw the expanded structural formula. So, the condensed structural formula actually gives you all the information you need to expand this structure. So, the expanded structural formula is going to be what we call the Lewis structure of the molecule, okay? So, it doesn't show, it doesn't represent bond angles, okay? So, just draw the Lewis structure. We see all of these carbons have to be bonded to each other because remember, carbon has to have four bonds, okay? So, this carbon is bonded to three H's. So, the fourth bond has to be to that other carbon. And remember, H can only bond to one thing, right? So, all of these H's have to be bonded to their parent carbon there or they wouldn't be stuck on that molecule. Is everybody okay with that? So, let's expand this. So, that's the first carbon. We call this a methyl group, a CH3 group, methyl group. Why? Because methane is CH4 and if you cut off an H there, we call it whatever. Okay, so next would be C with two H's like that. Is everybody okay with what we're doing? Does this make sense? So, the next one would be what? C and H there, and what's here? Good. And then next? Very good. And here? H. And here? H. And here? Very good, yes. So, that's the expanded structural formula. We also know about the Vesper theory, right? So, we could do the Vesper structure of this with all of these being 109.5 degree bonding. Okay? Let's go ahead and draw it over here. So, what I like to do is draw all the carbon atoms in a line. So, you won't have, because you're going to have to do backwards and forwards ones, you know? So, if you draw all the carbon atoms in a line, you do like a lot easier. And then, of course, the final two carbon atoms also have a hydrogen in that same plane. And then what you do is put your little bunny ears on, or bunny legs, I guess, depending on which carbon you are. Is everybody okay with that? Now remember, each one of these bond angles is effectively 109.5 degrees. That's what I want you to draw. And then the last type of formula we're going to learn in this problem is the bond line structure. Okay? This is the most convenient way to draw things, because you can draw them very quickly. Okay? And you can get a lot of detail in a very small amount of, I don't know, a small amount of space. It's a small amount of drawing. Okay? So, the bond line structure is essentially modeled after this Vesper structure. So, you can see, well, let's draw the bond line structure of beauty. Okay? It's like that. So, notice, it mirrors the carbon backbone there. Okay? We call that carbon string, the carbon backbone. Everybody's okay with that. So, notice what it's doing. It's saying each one of these points, or intersections, or ends of the line, kind of looks like Charlie Brown, if you know. Any end of a line or intersection of a point is a carbon atom. If that is the end of a line, then that carbon atom there is only attached to one other carbon atom. Okay? So, it's implied that the other three atoms that it's attached to are hydrogen atoms. Okay? So, this one has two hydrogen atoms. Why? Because it's a carbon that's got two bonds to it already. Is everybody okay with that? This one, how many hydrogen atoms does it have? Two, right? Why? Because carbon has four bonds altogether, and it's already showing two of those bonds. Okay? What about this one? Three. How many hydrogens? Three. Okay? Why? Because it's showing one bond already. Okay? So, it effectively looks exactly like this, except we're not identifying carbons and hydrogens. Okay? Let's just do one more thing, and we won't mess with this part. Okay? But let's just pretend that we have a different structure. Okay? And we'll draw this, this, and this, and according to that. Okay? And what we'll do is we'll add what we call a heteroatom, an atom that's not carbon or hydrogen. Let's add an OH group, kind of like what we did with the last problem. So, we'll add it right here, for example. So, if we wanted to, there we go. So, if we wanted to, and I always like to draw my lone pairs, just so I won't forget that they're there. Okay? Remember, all atoms, except for hydrogen in this structure, are going to have eight electrons around them. Okay? So, anyways, if I wanted to show this structure over here, what would I do? Well, I would take this structure and I would label it 1, carbon 1, carbon 2, carbon 3, carbon 4. Okay? And I would see that on carbon 3, there's an OH. Is everybody okay with that? So, I'll go over here after I've drawn this, carbon 1, 2, 3, 4, like that. And realize that on carbon 3, I want to change that to an OH. It didn't matter which side I put it on. Okay? Doesn't matter. Even though later you'll see that what we've made here is a stereo center if you take more chemistry, but for introductory chemistry, I wouldn't care which one you put it on. And then, to finalize to do this structure, to draw in what we call the bond line form, we would do that same thing, say carbon 1, 2, 3, 4, like that, so that OH is on carbon 3. So, we actually have to formally say OH, like that. And again, I like to put my lone pair electrons there just to remind myself. This also brings a good point up that every time a hydrogen is attached to a heteroatom, you have to show it, okay? So, it's only implied if it's attached to a carbon, okay? If it's attached to a heteroatom like an oxygen, nitrogen, sulfur, phosphorus, so on and so forth, you have to show it, okay? Are there any questions about this stuff so far? We'll do a couple more of these, and there's already a couple videos up there, okay? So, any questions before I turn off the video?