 Okay, ladies and gentlemen, let's compare these two molecules, okay, BECl2 and OCl2, okay. We're going to compare them in a number of ways because their molecular structure is actually different, okay, even though they've got the same number of atoms, okay, and they're arranged in a very similar way, okay. So, if we look at BE, right, how many valence electrons does it have? Well, first things first, what's the central atom here? BE, okay, so BE is the central atom, how do you know that just right off? Yeah, you could say that, that's a good way of thinking of it. Also, in this class you could think of it as chlorine can only make one bond, okay. So, we're not going to do any structures where we've got higher valences. So, halogens won't be making more than one bond, if you will, okay. So, BE's in the middle, right, and how many valence electrons does it have? Two, okay, BE's weird, it is a metal but it does share its electrons, okay, it's the one that does. So, in order to share, chlorine needs one of these two electrons, like that, and the other chlorine needs the other of the two, like that, okay. So, when we draw this, this structure here is both the Lewis structure and the perspective drawing, okay. Why is it different for water or OCl2, which is very similar to water? Let's draw what that looks like. O is the central atom, right, and it's got this, Cl, of course, it's going to be the same, it needs the one electron, so it's going to share like that, okay. So again, it looks very similar to what happened over here. The one thing that's different, I hope you can see, is the two lone pairs of electrons in on the central atom oxygen, okay, so when we draw the Lewis structure, that's the Lewis structure right there, okay, but it's not the perspective drawing, okay. The perspective drawing shows the bond angle, okay. This shows the bond angle over here, which is correct, because the bond angle here is linear or the structure is linear with a bond angle of 180 degrees. This bond is not linear and the angle is not 180 degrees. In fact, a good way to draw it is like this, okay, showing perspective, okay. Has anybody built this molecule? Show me this molecule, OCl2, somebody build it out there, yeah, well, kind of, yeah. I'd have preferred you to use the one with only the two holes in it, so this is what it looks like, right. So why does it look like this? So notice, I could have drawn it like this with both of those bonds in the plane of the board as well, let's do that as well, just so you know. So that's the same thing as that, both are perspective drawings, okay. One of them is drawn like that, the other one's like that, okay. What's the bond angle here, 104.5, how did you know that? Yeah, what did you memorize? Well, what angle did you memorize, how did you know it was 104.5? Well, how did you know that? Okay, that's how you know that, right, it's because you memorize the number of lone pairs give you this bond angle, that's what you're going to do, you're going to memorize those numbers anyways. But you got to memorize them relative to the number of lone pairs. So you notice both of these structures have three atoms, one central two peripheral, the two peripheral are the same atoms in both instances, but the angle or the structure is very different, right. So what did anybody, could you guys build beryllium chloride for me? And for yourselves? So the instructor has not okayed everybody's structure, so everybody show their structure to me. I use the light blue, do you guys have a light blue one? Okay, so you could have built it if you did though, right, I'm sure. So why is this again? Well, because there's no lone pair here, there's no lone pair that's going to force these things away from each other. Why do the lone pairs force the angles down, does anybody know? What if I have a negative charge and a negative charge, do they like to stick together? They like to repel each other, so electrons are they what charge? Negatively charged, other electrons are what? Negatively charged as well. So a lone pair of electrons is what charge essentially? Negatively charged, right. A bond is what? Is it positively charged? Well, there's no real charge, but if you wanted to talk about what composes a bond, right, what is it? Electrons, those have a negative charge overall, right. So lone pairs, they're essentially negatively charged, right. Bonds are negatively charged, why do the lone pairs force the bonds down? Because they're repelling each other, okay. They don't like to be anywhere near each other, that's what's happening. So that's bent and last thing, this is called linear, okay. On this, should we keep recording? Is it the same problem? Okay. Any questions on this problem?