 So this one should be fairly straightforward, I guess. Which of the following substances exhibits hydrogen bonding? And for those that do, draw two molecules of the substances with hydrogen bonds between them, clearly indicating the acceptor and donated portions of that hydrogen bond. OK? Is everybody OK with that? So I guess the first thing I would like you guys probably to do with these is draw the Lewis structure so you can see whether they hydrogen bonded. But hopefully you guys can tell me, through just looking up there, whether they have the ability to hydrogen bond, right? So does the top one even have the ability to hydrogen bond? No. Why not? It doesn't have nitrogen, oxygen, or fluorine in it. So even though it's got these hydrogens in it, right, it can't hydrogen bond. But I think it's still beneficial to draw the Lewis structure. So let's draw the Lewis structure of this molecule here, ethane. So hopefully you guys all drew it like this. And by now I don't think I need to draw it from this institute. So hopefully you guys can see, especially now, definitely there's no hydrogen, oxygen, hydrogen, hydrogen, or hydrogen bond. Is everybody OK with that? So let's just kind of delete this from the system and just look at these two. So do these ones potentially have the ability to hydrogen bond? Yes. Yes, right? Already we can say yes, because we see that they have both hydrogen and oxygen in them or hydrogen and nitrogen in this. OK? So it looks like this one's pretty much already showing us the Lewis structure, right? Let's draw the Lewis structure of this one over here. So CH3OH methanol. So when it's written like this, it's kind of showing you which atoms are bonded to which atoms. So here we're saying that that carbon is bonded to those three hydrogens. Is everybody OK with that? And also that carbon is bonded to that oxygen. Let's draw that. This group here is called a methyl group. CH3 group is called a methyl group. In fact, this molecule is known as methanol. But we said that carbon is bonded to that oxygen there. And that oxygen, of course, is bonded to that hydrogen. Is there anything missing on this Lewis structure? The lone pairs, right? So lone pairs on oxygen, there's two. OK, remember, this is just the Lewis structure. So this doesn't tell us any structural information except for where the atoms are bonded to each other. But we see that there's this oxygen-hydrogen bond. Is everybody OK with that? So when we see that, we should realize automatically that this thing is going to be able to hydrogen bond. OK? And so it wants us to draw a hydrogen bond to another member of the same species. OK, so let's do that. So hopefully you guys have already done this. So again, this is just another way to draw methanol. It's kind of like on its side. And I'm going to draw. Remember, those intermolecular forces we draw is kind of dashed lines. So who didn't remember that? So this itself would be a hydrogen bond. And it wants us to label the hydrogen bond acceptors and donators. So in this hydrogen bond, if we have a hydrogen bond, there has to be an acceptor and a donator. So what portion is the acceptor of the hydrogen bond? The oxygen lone pair. So the oxygen lone pair is the acceptor. So in fact, this lone pair can make a hydrogen bond with another one. So we'll just say there's another one down here like that. And we'll just label this acceptor. For the hydrogen bond that we're directly showing here, this is the actual acceptor. This over here, of course, is the donor of the hydrogen bond. And of course, you've got these two more acceptors here. So if I asked you for the number of acceptors and the number of donors in this molecule, what would you say? So let's say, so hydrogen bond acceptors, how many are there in that one? Two in one molecule. That's all I'm looking for. How many are in one molecule? Two. Why? Because there's only two oxygen lone pairs where that oxygen, well, it doesn't have to be bonded to the hydrogen, but there's two oxygen lone pairs, one of those really electronegative bonds, so two. And how many donors do I have in one molecule? Just one, right? Why? Only one? Because there's only one hydrogen bonded to one of those electronegative bonds. So those electronegative atoms, they have those lone pairs, and they'll always be hydrogen bonded acceptors, no matter what they're bonded to. So in other words, when we look at this structure, hopefully you can see that there's a portion that has hydrogen bonded acceptors, but not donors. So let's draw this one out from this kind of condensed structure to its big Lewis structure. And again, this is just the Lewis structure. I gave away the lone pairs. So instead of drawing another one of these molecules and drawing a bunch of hydrogen bonds, why don't we just figure out how many donors and how many acceptors this molecule has? So who wants to tell me how many acceptors this thing has? Three, why? Three lone pairs on those particular electronegative atoms that would look, right? So the acceptors would be here, here, and here. And what about donors? How many hydrogen bond donors does this have? Two, right? Why didn't you say these ones? Well, I'm assuming that you're saying these two hydrogens, right? Why wouldn't these three be if they're not attached to one of those collections? So what if we noticed about this molecule, right? There's an atom that has acceptors, but not donors. This top oxygen up there, what we say is the carbonyl oxygen. This thing here is a carbonyl C double bond O, where it's singly bonded to 2O. You'll learn more about that in organic. Any questions on that one? What exactly is that? Well, it's one of those van der Waals forces, the binomial-agular forces. Yeah, so there's that partial positive. It's the difference of electronegativity. So those really electronegative atoms really want those electrons. And hydrogen likes to give them up. And in fact, what you'll see, I mean, you know about strong acids. You know about strong masses. Those are molecules that have a hydrogen atom attached to a really electronegative atom that can form a polyatomic ion that's more stable than the actual uncharged structure. So it would prefer to have that hydrogen missing than have it there. So that's what makes a strong acid, is that you have this what we call conjugate base that's actually more stable than the acid itself. The conjugate base being the polyatomic ion that's formed from the loss of the hydrogen atom. I'll show you right now.