1 00:00:16,767 --> 00:00:18,302 Let's get started. 2 00:00:18,302 --> 00:00:20,471 We'll cut right to the chase. 3 00:00:20,471 --> 00:00:25,109 How did it go on the exam? 4 00:00:25,109 --> 00:00:25,809 I crushed that. 5 00:00:25,809 --> 00:00:27,111 I heard I crushed that. 6 00:00:27,111 --> 00:00:27,878 Yeah. 7 00:00:27,878 --> 00:00:28,512 Look at that. 8 00:00:32,649 --> 00:00:37,621 So you guys rocked it on exam one, and I'm very proud of you, 9 00:00:37,621 --> 00:00:41,925 and I think this is awesome. 10 00:00:41,925 --> 00:00:45,362 The average was actually really high, which is great. 11 00:00:45,362 --> 00:00:50,901 It means, to me, that you guys have learned the materials 12 00:00:50,901 --> 00:00:53,370 that we want you to learn in the first third of this class. 13 00:00:58,509 --> 00:01:02,713 You know, this is also a chance that if you didn't get up 14 00:01:02,713 --> 00:01:04,480 into this range, you're here or down here, 15 00:01:04,480 --> 00:01:05,949 or even if you're up here, and there 16 00:01:05,949 --> 00:01:07,985 are a couple of problems you didn't quite get, 17 00:01:07,985 --> 00:01:11,422 this is the time to go back and say, what did I miss? 18 00:01:11,422 --> 00:01:11,922 Right. 19 00:01:11,922 --> 00:01:13,090 How did I misinterpret? 20 00:01:13,090 --> 00:01:16,794 Or what did I miss, and go back over it now. 21 00:01:16,794 --> 00:01:19,096 Solidify this knowledge. 22 00:01:19,096 --> 00:01:20,097 Why? 23 00:01:20,097 --> 00:01:23,300 Because of what's coming next. 24 00:01:25,869 --> 00:01:27,971 And I really want to contextualize 25 00:01:27,971 --> 00:01:32,843 this with something really important to me. 26 00:01:32,843 --> 00:01:34,545 And that's bread. 27 00:01:34,545 --> 00:01:41,685 Now, if you want to get the best ride in town you go to Bricco. 28 00:01:41,685 --> 00:01:44,354 All right, and I really actually strongly 29 00:01:44,354 --> 00:01:47,390 encourage you all to go to Bricco, because it's true. 30 00:01:47,390 --> 00:01:50,594 It's really the best bread in town. 31 00:01:50,594 --> 00:01:51,829 There's Frank. 32 00:01:51,829 --> 00:01:54,598 He founded Bricco. 33 00:01:54,598 --> 00:01:55,532 It's in the South end. 34 00:01:55,532 --> 00:01:58,469 It's amazing. 35 00:01:58,469 --> 00:02:01,672 But you notice his ingredients, there's 36 00:02:01,672 --> 00:02:05,576 only seven ingredients in the bread at Bricco. 37 00:02:05,576 --> 00:02:09,880 There's salt, right, yeast, water. 38 00:02:09,880 --> 00:02:11,181 There. 39 00:02:11,181 --> 00:02:13,016 Anybody know what farina is? 40 00:02:13,016 --> 00:02:13,717 Flour. 41 00:02:13,717 --> 00:02:17,054 OK, crusca, it's like kind of wheat stuff. 42 00:02:17,054 --> 00:02:20,791 Oil and passione. 43 00:02:20,791 --> 00:02:22,960 Passione. 44 00:02:22,960 --> 00:02:23,460 Passion. 45 00:02:23,460 --> 00:02:25,796 It's the thing he's holding. 46 00:02:25,796 --> 00:02:28,599 That's ingredient number seven at Bricco, which 47 00:02:28,599 --> 00:02:29,700 is the best friend in town. 48 00:02:29,700 --> 00:02:31,268 Now, here's my point. 49 00:02:34,371 --> 00:02:39,643 I need you guys to keep bringing the passion to this class. 50 00:02:39,643 --> 00:02:41,645 You should be bringing the passion to everything 51 00:02:41,645 --> 00:02:45,682 you do, because that's what we do at MIT, right? 52 00:02:45,682 --> 00:02:47,951 That's how we approach everything we do. 53 00:02:47,951 --> 00:02:50,721 But I need you not to say, well, I did really well in exam one, 54 00:02:50,721 --> 00:02:52,456 and now I can kind of phone it in. 55 00:02:52,456 --> 00:02:54,291 That's not the time to do it. 56 00:02:54,291 --> 00:02:55,025 Trust me. 57 00:02:55,025 --> 00:03:00,497 Because now we're going into the next phase, the next third, 58 00:03:00,497 --> 00:03:03,400 a little bit less than a third of the class where 59 00:03:03,400 --> 00:03:06,403 we're going to come maybe out of some of our comfort zones. 60 00:03:06,403 --> 00:03:06,904 All right. 61 00:03:06,904 --> 00:03:08,839 So some of you have seen a lot of the material 62 00:03:08,839 --> 00:03:10,140 that we've already covered. 63 00:03:10,140 --> 00:03:12,576 Some of you haven't. 64 00:03:12,576 --> 00:03:14,378 And some of you may have seen some 65 00:03:14,378 --> 00:03:15,879 of the material we're about to cover 66 00:03:15,879 --> 00:03:17,681 in the next week or two, shapes of molecules 67 00:03:17,681 --> 00:03:20,284 and molecular orbital theory, hybridization. 68 00:03:20,284 --> 00:03:23,220 But then we're going to go into crystals, 69 00:03:23,220 --> 00:03:25,055 and we're going to take molecular orbitals, 70 00:03:25,055 --> 00:03:27,124 and we're going to make solid orbitals out 71 00:03:27,124 --> 00:03:29,459 of them, which are called bands, which is going 72 00:03:29,459 --> 00:03:30,827 to give us semiconductors. 73 00:03:30,827 --> 00:03:34,364 And then we're going to dope those with chemistry. 74 00:03:34,364 --> 00:03:35,933 All sorts of stuff. 75 00:03:35,933 --> 00:03:39,670 So keep up the passion, please. 76 00:03:39,670 --> 00:03:42,873 That's why I was showing you Frank and Bricco. 77 00:03:42,873 --> 00:03:43,974 Keep up the passion. 78 00:03:43,974 --> 00:03:49,079 OK, now today, we're going to cover a really important follow 79 00:03:49,079 --> 00:03:54,851 up to Lewis, which is, how to predict 80 00:03:54,851 --> 00:03:56,753 what shape a molecule will be. 81 00:04:00,157 --> 00:04:04,528 And so, you know, if I take, so for example, H2Be and H20, 82 00:04:04,528 --> 00:04:06,530 now those look-- 83 00:04:06,530 --> 00:04:22,746 right, OK, so, H Be H and H O H, right, from Lewis, 84 00:04:22,746 --> 00:04:26,283 we don't really know why they both looked that way. 85 00:04:26,283 --> 00:04:29,286 Are they both linear? 86 00:04:29,286 --> 00:04:31,121 Are the ones below both linear? 87 00:04:31,121 --> 00:04:34,191 How do we tell what shape they are? 88 00:04:34,191 --> 00:04:35,692 And as I'll tell you about today, 89 00:04:35,692 --> 00:04:41,331 so I'm going to give you a way to do that and then 90 00:04:41,331 --> 00:04:43,533 a recipe, another recipe, just like Lewis, 91 00:04:43,533 --> 00:04:48,605 and then, we're going to talk about the goody bag, which 92 00:04:48,605 --> 00:04:55,612 allows you to touch and feel the shapes. 93 00:04:55,612 --> 00:04:59,616 You can't-- we're going beyond 2D. 94 00:04:59,616 --> 00:05:00,884 We're coming out of the board. 95 00:05:00,884 --> 00:05:01,818 We're going 3D. 96 00:05:01,818 --> 00:05:03,420 You got to hold it in your hand. 97 00:05:03,420 --> 00:05:06,823 Now, unfortunately, we couldn't buy like 500 kits 98 00:05:06,823 --> 00:05:08,191 that are this big. 99 00:05:08,191 --> 00:05:10,727 But I'll pass these around, because you can just 100 00:05:10,727 --> 00:05:12,896 feel-- in these molecules, you can just 101 00:05:12,896 --> 00:05:17,234 feel that if I do this, it's a different molecule. 102 00:05:17,234 --> 00:05:20,203 If I rotate that, it's a different molecule. 103 00:05:20,203 --> 00:05:23,507 It's actually going to have different properties. 104 00:05:23,507 --> 00:05:27,644 And so that's what we learned today. 105 00:05:27,644 --> 00:05:32,249 Lewis, this is just all flattened into the board. 106 00:05:32,249 --> 00:05:33,884 Doesn't tell me enough. 107 00:05:33,884 --> 00:05:37,854 It doesn't tell-- I need to know what those-- 108 00:05:37,854 --> 00:05:39,623 is it like that? 109 00:05:39,623 --> 00:05:40,157 I don't know. 110 00:05:40,157 --> 00:05:41,992 Do the yellow things want to be that close, 111 00:05:41,992 --> 00:05:45,329 or should it maybe be like that or like that? 112 00:05:45,329 --> 00:05:47,097 You see how when you can do this? 113 00:05:47,097 --> 00:05:51,268 I could do this for hours honestly. 114 00:05:51,268 --> 00:05:53,203 So I'll pass these around. 115 00:05:53,203 --> 00:05:55,038 And I'm certain at some point we're 116 00:05:55,038 --> 00:05:58,342 going to hear loud clinking sounds of these balls falling 117 00:05:58,342 --> 00:05:58,842 apart. 118 00:05:58,842 --> 00:06:00,577 They're not held together too well. 119 00:06:00,577 --> 00:06:03,680 Please try to not-- 120 00:06:03,680 --> 00:06:05,449 just play with it a little bit. 121 00:06:05,449 --> 00:06:08,285 Right, and then your kit is a smaller version of that. 122 00:06:08,285 --> 00:06:09,853 OK, so how do we do this? 123 00:06:09,853 --> 00:06:13,757 How do I tell you what shape that should be? 124 00:06:13,757 --> 00:06:18,995 Well, we have a way to do this, and it's got a name even. 125 00:06:21,631 --> 00:06:27,504 So just to contrast, Lewis is what we did last. 126 00:06:27,504 --> 00:06:35,879 And Lewis gives me the numbers and type of bonds, OK. 127 00:06:39,082 --> 00:06:40,550 The number and type of bonds. 128 00:06:40,550 --> 00:06:43,220 But now, I've got a way that's called 129 00:06:43,220 --> 00:06:49,593 Valence-Shell Electron-Pair Repulsion model, VSEPR, VSEPR. 130 00:06:49,593 --> 00:06:54,231 But see, chemists are-- if I haven't conveyed this 131 00:06:54,231 --> 00:06:58,702 before, chemists are really good at naming things. 132 00:06:58,702 --> 00:07:06,009 So it could be valence electron shell pair repulsion model. 133 00:07:06,009 --> 00:07:06,676 It's not. 134 00:07:06,676 --> 00:07:07,577 But it could be. 135 00:07:07,577 --> 00:07:09,646 And if it weren't we'd call it VESPR. 136 00:07:09,646 --> 00:07:11,014 It would sound a lot better. 137 00:07:11,014 --> 00:07:13,383 Right, and so that's what we call it 138 00:07:13,383 --> 00:07:16,219 even though we write VSEPR. 139 00:07:16,219 --> 00:07:18,855 So we write it like this, but we say vesper, 140 00:07:18,855 --> 00:07:21,224 because this is chemistry. 141 00:07:24,094 --> 00:07:25,395 And this gives us the shape. 142 00:07:25,395 --> 00:07:33,103 Now, it's based on actually a very straightforward premise, 143 00:07:33,103 --> 00:07:37,240 which is that electrons repel each other, something we 144 00:07:37,240 --> 00:07:39,576 already knew. 145 00:07:39,576 --> 00:07:54,024 OK, electrons repel each other, and the stable arrangement-- 146 00:07:54,024 --> 00:07:56,058 I hear that molecule changing shape. 147 00:07:56,058 --> 00:07:58,929 It makes me happy. 148 00:07:58,929 --> 00:08:04,534 OK, the stable arrangement minimizes-- 149 00:08:04,534 --> 00:08:06,503 now, this makes sense right? 150 00:08:06,503 --> 00:08:09,673 Minimizes the repulsions. 151 00:08:09,673 --> 00:08:13,009 OK, that's really the whole premise of VSEPR. 152 00:08:13,009 --> 00:08:15,612 VSEPR theory is a way-- it's a very simple recipe 153 00:08:15,612 --> 00:08:20,750 that we will learn and apply that is based on this premise. 154 00:08:20,750 --> 00:08:22,118 We already talked about electrons 155 00:08:22,118 --> 00:08:26,256 repelling each other in atoms, right, and in a bond. 156 00:08:26,256 --> 00:08:28,425 And now we use the same idea that electrons 157 00:08:28,425 --> 00:08:32,729 repel each other for a molecule, right, within a molecule. 158 00:08:32,729 --> 00:08:34,164 OK, good. 159 00:08:34,164 --> 00:08:35,799 But we need to rank order this. 160 00:08:35,799 --> 00:08:37,000 We need to rank order this. 161 00:08:37,000 --> 00:08:38,969 And so we have a rank order. 162 00:08:38,969 --> 00:08:45,375 And you'll see kind of why, as we go. 163 00:08:45,375 --> 00:08:46,776 I'll tell it to you right now. 164 00:08:46,776 --> 00:08:48,445 And I need abbreviations, because I 165 00:08:48,445 --> 00:08:51,515 don't want to keep writing bonding pair and lone pair. 166 00:08:51,515 --> 00:08:55,785 So I'm going to say that a bonding pair, a bonding pair, 167 00:08:55,785 --> 00:08:56,920 oh what's a bonding pair? 168 00:08:56,920 --> 00:09:00,724 Well, it's the two electrons in a bond right there. 169 00:09:00,724 --> 00:09:02,259 That's a bonding pair. 170 00:09:02,259 --> 00:09:04,060 OK, good. 171 00:09:04,060 --> 00:09:09,966 So a bonding pair, to save time, we're going to write as a BP. 172 00:09:09,966 --> 00:09:13,370 And a lone pair, what's a long pair? 173 00:09:13,370 --> 00:09:15,539 Well, we already know that. 174 00:09:15,539 --> 00:09:20,577 A lone pair is right there. 175 00:09:20,577 --> 00:09:24,147 A non-bonding pair, a lone pair, an LP. 176 00:09:24,147 --> 00:09:25,081 OK, good. 177 00:09:25,081 --> 00:09:31,288 Now, this allows me, now that I have this very important key, 178 00:09:31,288 --> 00:09:33,189 I can tell you what the repulsion 179 00:09:33,189 --> 00:09:37,427 order is without writing out bonding and lone all the time. 180 00:09:37,427 --> 00:09:43,700 Repulsion order and this is what we follow in VSEPR. 181 00:09:43,700 --> 00:09:49,306 OK, so we're going to go the lowest repulsion is between two 182 00:09:49,306 --> 00:09:53,510 bonding pairs, bonding pair to bonding pair. 183 00:09:53,510 --> 00:09:58,248 And the medium medium, OK, so the next in our list 184 00:09:58,248 --> 00:10:06,756 is bonding pair to lone pair, and the highest 185 00:10:06,756 --> 00:10:09,526 is between two lone pairs. 186 00:10:09,526 --> 00:10:13,663 All I'm telling you is in this ordering 187 00:10:13,663 --> 00:10:18,602 is that OK, electrons repel each other, yeah, got it, 188 00:10:18,602 --> 00:10:20,604 but there's an ordering to it. 189 00:10:20,604 --> 00:10:23,673 If I'm a lone pair, and I see another lone pair, 190 00:10:23,673 --> 00:10:25,675 that I'm more repelled. 191 00:10:25,675 --> 00:10:27,911 Those two things are more repelled, then 192 00:10:27,911 --> 00:10:29,613 a lone pair and a bonding pair, which 193 00:10:29,613 --> 00:10:31,581 are more repelled than two bonding pairs, 194 00:10:31,581 --> 00:10:33,583 and we got one more thing we got to think about, 195 00:10:33,583 --> 00:10:38,955 because you see the bonding pairs can be single, double, 196 00:10:38,955 --> 00:10:40,724 or triple. 197 00:10:40,724 --> 00:10:43,059 And so those have a rank order, which also 198 00:10:43,059 --> 00:10:45,929 makes a lot of sense, right. 199 00:10:45,929 --> 00:10:52,736 So like one bonding pair would have a single bond. 200 00:10:52,736 --> 00:10:55,105 With a single bond would have a lower repulsion 201 00:10:55,105 --> 00:11:03,046 than a double bond, which would have less repulsion 202 00:11:03,046 --> 00:11:05,482 than a triple bond, right? 203 00:11:05,482 --> 00:11:07,617 But that makes a lot of sense, right? 204 00:11:07,617 --> 00:11:11,388 You're putting more electrons in the bond. 205 00:11:11,388 --> 00:11:14,224 And so there's more stuff to repel. 206 00:11:14,224 --> 00:11:16,726 Right, so if I'm talking about bonding pairs, 207 00:11:16,726 --> 00:11:19,396 there is also a sub order. 208 00:11:19,396 --> 00:11:20,764 OK, that makes sense, right? 209 00:11:20,764 --> 00:11:27,470 So this is like a single bond line, two lines, no room, 210 00:11:27,470 --> 00:11:29,372 three lines, right? 211 00:11:31,741 --> 00:11:32,242 All right. 212 00:11:32,242 --> 00:11:36,746 Now this frames the VSEPR model. 213 00:11:36,746 --> 00:11:39,683 Now let's apply it, and the rules are actually 214 00:11:39,683 --> 00:11:41,151 really pretty straightforward. 215 00:11:41,151 --> 00:11:42,552 So what we're going to do is we're 216 00:11:42,552 --> 00:11:45,455 going to build our understanding by applying this 217 00:11:45,455 --> 00:11:47,924 to some examples, because it's exactly the same thing we 218 00:11:47,924 --> 00:11:50,727 did with Lewis. 219 00:11:50,727 --> 00:11:54,297 OK, so I'm going to start my recipe with the first three 220 00:11:54,297 --> 00:11:55,632 ingredients. 221 00:11:55,632 --> 00:11:58,568 Passion is always there, too. 222 00:11:58,568 --> 00:12:01,671 But these are the first three ingredients of my VSEPR recipe. 223 00:12:01,671 --> 00:12:03,206 First, I write the structure. 224 00:12:03,206 --> 00:12:04,174 We know how to do that. 225 00:12:04,174 --> 00:12:05,408 We learn how to do that. 226 00:12:05,408 --> 00:12:08,712 And then I'm going to classify the pairs of electrons 227 00:12:08,712 --> 00:12:09,813 as bonding or non-bonding. 228 00:12:09,813 --> 00:12:13,083 So I'm going to just label them like that. 229 00:12:13,083 --> 00:12:15,652 And then I'm going to maximize the separation between domains 230 00:12:15,652 --> 00:12:19,189 and pay attention to these rules, 231 00:12:19,189 --> 00:12:21,324 and I'm going to start a little bit 232 00:12:21,324 --> 00:12:24,394 of a table over here, number-- 233 00:12:24,394 --> 00:12:27,263 because we're going to fill this table out-- number 234 00:12:27,263 --> 00:12:31,101 of electron regions. 235 00:12:31,101 --> 00:12:34,037 OK, let's do this. 236 00:12:34,037 --> 00:12:39,042 You know when I do this, there's nothing but fun coming. 237 00:12:39,042 --> 00:12:40,577 Nothing but fun. 238 00:12:40,577 --> 00:12:42,979 I went all the way, all the way over. 239 00:12:42,979 --> 00:12:43,646 Why? 240 00:12:43,646 --> 00:12:46,282 Because I need some space. 241 00:12:46,282 --> 00:12:50,920 Now, here, we're going to say electron pair geometry. 242 00:12:50,920 --> 00:12:54,190 We'll be talking about this today, geometry. 243 00:12:54,190 --> 00:12:55,091 OK, good. 244 00:12:57,994 --> 00:13:05,068 And then, here, OK, now this is sort of the molecular-- 245 00:13:05,068 --> 00:13:09,072 molecular geometry. 246 00:13:09,072 --> 00:13:12,776 So I'm going from-- 247 00:13:12,776 --> 00:13:16,679 I'm going from counting electron regions 248 00:13:16,679 --> 00:13:20,884 and labeling what kind they are to a geometry of the electron 249 00:13:20,884 --> 00:13:25,889 cloud around things to an actual molecular shape, which 250 00:13:25,889 --> 00:13:30,693 is what VSEPR gives us, and to know why is this so wide, well, 251 00:13:30,693 --> 00:13:32,929 because there's options in here. 252 00:13:32,929 --> 00:13:39,135 Right, because I could have no lone pairs. 253 00:13:39,135 --> 00:13:40,904 All right. 254 00:13:40,904 --> 00:13:46,976 I could have one lone pair. 255 00:13:46,976 --> 00:13:49,379 And this will all make a lot of sense. 256 00:13:49,379 --> 00:13:53,349 Two lone pairs and so on. 257 00:13:53,349 --> 00:13:55,151 We'll keep going as we get there. 258 00:13:55,151 --> 00:14:00,223 OK, so I'm going to start with a very simple case. 259 00:14:00,223 --> 00:14:02,525 I'm going to start with this. 260 00:14:02,525 --> 00:14:03,226 Right. 261 00:14:03,226 --> 00:14:06,996 And then we're going to put some stuff into that table as we go. 262 00:14:06,996 --> 00:14:07,497 All right. 263 00:14:07,497 --> 00:14:13,503 So look if I have H, Be H, then that's already 0.1. 264 00:14:13,503 --> 00:14:15,471 I'm going to write, just like I did with Lewis, 265 00:14:15,471 --> 00:14:17,841 I'm going to write the number of the recipe 266 00:14:17,841 --> 00:14:19,475 next to what I'm doing on the board. 267 00:14:19,475 --> 00:14:21,544 OK, so one, write Lewis structure. 268 00:14:21,544 --> 00:14:23,213 I did it. 269 00:14:23,213 --> 00:14:24,280 OK, good. 270 00:14:24,280 --> 00:14:31,421 Now two, I've got two electron pairs. 271 00:14:31,421 --> 00:14:34,724 OK, and they're both bonding. 272 00:14:34,724 --> 00:14:37,527 Both are BP. 273 00:14:37,527 --> 00:14:41,231 OK, and so I've got two BP domains. 274 00:14:41,231 --> 00:14:43,499 And as you can see, I've got no LP domains. 275 00:14:46,736 --> 00:14:52,742 And so three, this is going to be max separation, 276 00:14:52,742 --> 00:14:57,747 max sep will have to be linear. 277 00:14:57,747 --> 00:14:59,215 There's just no other way about it. 278 00:14:59,215 --> 00:15:01,718 I've only got two electron domains. 279 00:15:01,718 --> 00:15:03,519 I've got no lone pairs. 280 00:15:03,519 --> 00:15:05,655 So two bonding domains, two electron domains. 281 00:15:05,655 --> 00:15:06,689 It's got to be linear. 282 00:15:06,689 --> 00:15:08,858 That's the only way I can go. 283 00:15:08,858 --> 00:15:11,394 So if the number of electron regions is two, 284 00:15:11,394 --> 00:15:18,668 which it is for BeH2, OK, and and then the number of-- 285 00:15:18,668 --> 00:15:24,874 the electron pair geometry is linear, right, 286 00:15:24,874 --> 00:15:27,310 because that maximizes the separations. 287 00:15:27,310 --> 00:15:31,547 And there is no lone pairs, and so it's linear. 288 00:15:31,547 --> 00:15:35,018 You say, well, that really seems redundant. 289 00:15:35,018 --> 00:15:37,353 It is in this case. 290 00:15:37,353 --> 00:15:42,525 It's not going to stay that way, not going to stay that way. 291 00:15:42,525 --> 00:15:43,426 OK. 292 00:15:43,426 --> 00:15:44,060 Good. 293 00:15:44,060 --> 00:15:46,362 One lone pair, no. 294 00:15:46,362 --> 00:15:47,897 No lone pairs. 295 00:15:47,897 --> 00:15:53,469 I mean, if I had two electron regions total, OK, 296 00:15:53,469 --> 00:15:56,539 and one of them was a lone pair, it's kind of boring. 297 00:15:56,539 --> 00:15:58,540 I mean, you know, if this were a lone pair here, 298 00:15:58,540 --> 00:16:00,944 instead of a bond, well, clearly it's linear. 299 00:16:00,944 --> 00:16:03,046 There's only two atoms. 300 00:16:03,046 --> 00:16:05,081 That's kind of the simplest case. 301 00:16:05,081 --> 00:16:08,451 We won't really talk about that. 302 00:16:08,451 --> 00:16:08,952 Good. 303 00:16:08,952 --> 00:16:11,621 OK, now it's the same kind of thing. 304 00:16:11,621 --> 00:16:14,791 Let me just make sure that there's no confusion here. 305 00:16:14,791 --> 00:16:19,128 And let's not leave this up. 306 00:16:19,128 --> 00:16:21,931 But if I had-- 307 00:16:21,931 --> 00:16:24,667 let's say I go back to my first slide there. 308 00:16:24,667 --> 00:16:26,869 OK, so what if I had this one. 309 00:16:26,869 --> 00:16:28,805 It looks more complicated. 310 00:16:28,805 --> 00:16:31,674 Right, it looks more complicated. 311 00:16:31,674 --> 00:16:43,453 So now, OK, so OK, step one O and here you go, here you go. 312 00:16:43,453 --> 00:16:45,121 And there's a point I want to make here, 313 00:16:45,121 --> 00:16:48,691 because if I count up the bonding pair 314 00:16:48,691 --> 00:16:52,662 domains and the lone pair domains on this one, 315 00:16:52,662 --> 00:16:57,266 all right, say well, OK, I've got the bonding pairs here. 316 00:16:57,266 --> 00:16:58,368 I've got some BPs. 317 00:16:58,368 --> 00:17:01,904 I've got two BP domains right? 318 00:17:01,904 --> 00:17:07,542 Here and here, just like I did in H Be H. 319 00:17:07,542 --> 00:17:12,515 But oh, I've got all these lone pairs now. 320 00:17:12,515 --> 00:17:14,817 Don't I have four lone pairs? 321 00:17:14,817 --> 00:17:15,818 No. 322 00:17:15,818 --> 00:17:18,887 And the reason is we have to pick an atom. 323 00:17:18,887 --> 00:17:21,590 In VSEPR, we have to pick an atom. 324 00:17:21,590 --> 00:17:23,459 We're doing this around an atom. 325 00:17:23,459 --> 00:17:25,694 VSEPR applies around an atom. 326 00:17:25,694 --> 00:17:30,633 You pick a central, and I picked carbon as my central atom. 327 00:17:30,633 --> 00:17:33,636 And then you apply VSEPR. 328 00:17:33,636 --> 00:17:36,873 So there's no lone pairs around the carbon. 329 00:17:36,873 --> 00:17:40,510 That doesn't matter for the shape around carbon. 330 00:17:40,510 --> 00:17:42,345 OK, that's really important. 331 00:17:42,345 --> 00:17:44,447 So I pick my central atom. 332 00:17:44,447 --> 00:17:48,418 So now I know there's no lone pairs, no LP, 333 00:17:48,418 --> 00:17:50,653 because central atom. 334 00:17:50,653 --> 00:17:53,022 You know what I mean, central atom. 335 00:17:56,592 --> 00:17:58,995 And then finally, three, we're going 336 00:17:58,995 --> 00:18:02,799 to get linear because, again, there's 337 00:18:02,799 --> 00:18:05,935 only two electron domains. 338 00:18:05,935 --> 00:18:07,537 There's going to electron domains, 339 00:18:07,537 --> 00:18:10,506 and the only geometry really that you can take in this case 340 00:18:10,506 --> 00:18:11,707 is linear. 341 00:18:11,707 --> 00:18:13,643 No lone pairs, two electron domains. 342 00:18:13,643 --> 00:18:14,477 Good. 343 00:18:14,477 --> 00:18:17,280 And now you know it's about to get fun, 344 00:18:17,280 --> 00:18:20,817 because now we're going to go to something more. 345 00:18:20,817 --> 00:18:21,984 Let's go back to our recipe. 346 00:18:21,984 --> 00:18:22,685 There it is. 347 00:18:22,685 --> 00:18:31,327 OK, so I'm going to make room here and do my next one. 348 00:18:31,327 --> 00:18:33,262 I'm going to go a little bit more complicated. 349 00:18:33,262 --> 00:18:35,431 So now I've got BF3. 350 00:18:35,431 --> 00:18:44,974 So B, and we're going to go F, F, F. 351 00:18:44,974 --> 00:18:48,177 And we know we got all these lone pairs out on the F's. 352 00:18:48,177 --> 00:18:50,279 Remember this is one that's electron deficient. 353 00:18:50,279 --> 00:18:53,950 We talked about this last week, electron deficient. 354 00:18:53,950 --> 00:18:56,619 So the boron is happy even though it's only 355 00:18:56,619 --> 00:18:57,787 got those three bonds. 356 00:18:57,787 --> 00:18:59,188 The question is, what's the shape? 357 00:18:59,188 --> 00:19:01,457 We've been drawing these structures like this in 2D. 358 00:19:01,457 --> 00:19:04,327 What's the real shape? 359 00:19:04,327 --> 00:19:08,164 Now we can apply VSEPR because that's step one. 360 00:19:08,164 --> 00:19:15,004 Step two is that I've got three bonding pairs, 3 BP, right, 361 00:19:15,004 --> 00:19:18,374 and no LP. 362 00:19:18,374 --> 00:19:19,675 OK. 363 00:19:19,675 --> 00:19:24,514 And so now if I have three electron domains, 364 00:19:24,514 --> 00:19:29,485 three electron domains, which I have, then the max separation 365 00:19:29,485 --> 00:19:36,559 for this case, max sep is going to be for them to spread out 366 00:19:36,559 --> 00:19:38,294 in a trigonal plane. 367 00:19:38,294 --> 00:19:40,396 OK, so that's what they're going to do. 368 00:19:40,396 --> 00:19:45,101 And that is called trigonal planar. 369 00:19:45,101 --> 00:19:49,605 It has a name trigonal planar. 370 00:19:49,605 --> 00:19:54,510 So you know, it's kind of-- 371 00:19:54,510 --> 00:19:56,312 planar. 372 00:19:56,312 --> 00:19:58,314 So it's kind of right, but it's not quite right 373 00:19:58,314 --> 00:20:00,149 because I drew with 90 degree angles, 374 00:20:00,149 --> 00:20:01,784 and that's not what they are going to do 375 00:20:01,784 --> 00:20:04,954 to maximize their spacing here. 376 00:20:04,954 --> 00:20:07,690 They're going to go at angles like that. 377 00:20:07,690 --> 00:20:09,892 All right, they're going to find 120. 378 00:20:09,892 --> 00:20:15,064 So if I have three electron regions, here we go, then-- 379 00:20:15,064 --> 00:20:16,232 now I had three-- 380 00:20:16,232 --> 00:20:18,534 OK, so the electron pair geometry. 381 00:20:18,534 --> 00:20:19,802 Why is this different? 382 00:20:19,802 --> 00:20:21,804 You will see in a minute. 383 00:20:21,804 --> 00:20:27,009 The electron pair geometry covers BPs and LPs, 384 00:20:27,009 --> 00:20:30,580 but in this case, there's only BPs. 385 00:20:30,580 --> 00:20:31,113 Fine. 386 00:20:31,113 --> 00:20:32,982 There's still only three. 387 00:20:32,982 --> 00:20:36,252 Right, and so it's trigonal planar. 388 00:20:39,889 --> 00:20:43,326 Trigonal planar. 389 00:20:43,326 --> 00:20:46,395 And guess what, if there is no LPs-- 390 00:20:46,395 --> 00:20:49,198 OK, so the structure that the molecule takes 391 00:20:49,198 --> 00:20:52,668 or those electron domains takes is trigonal planar. 392 00:20:52,668 --> 00:20:55,571 The structure that the molecule takes if there is no LPs 393 00:20:55,571 --> 00:20:57,006 is also trigonal planar. 394 00:20:59,575 --> 00:21:04,180 But now, the moment we've been waiting for 395 00:21:04,180 --> 00:21:07,316 is what happens when that's not true, 396 00:21:07,316 --> 00:21:09,151 and you've got a lone pair. 397 00:21:09,151 --> 00:21:11,020 So again, we're going to do this by example. 398 00:21:14,757 --> 00:21:17,960 OK, and so my next example is formaldehyde, 399 00:21:17,960 --> 00:21:23,833 which is something we love to talk about when we did Lewis. 400 00:21:23,833 --> 00:21:27,303 So CH2O. 401 00:21:27,303 --> 00:21:30,339 OK, so the Lewis structure for this looks like this. 402 00:21:30,339 --> 00:21:34,310 Right, we drew this before, O, it's got the lone pairs out 403 00:21:34,310 --> 00:21:47,123 here, and then there's H and another H. That's formaldehyde. 404 00:21:47,123 --> 00:21:49,125 OK, now hold on. 405 00:21:49,125 --> 00:21:52,962 But there's no-- are there any lone pairs here? 406 00:21:52,962 --> 00:21:54,897 There's no lone pairs. 407 00:21:54,897 --> 00:21:55,798 There's no lone pairs. 408 00:21:55,798 --> 00:21:56,966 So hold on. 409 00:21:56,966 --> 00:22:02,972 If I go to two, I've got three bonding pairs 410 00:22:02,972 --> 00:22:05,007 and zero lone pairs. 411 00:22:05,007 --> 00:22:08,711 It looks a whole lot like BF3, but it's different. 412 00:22:08,711 --> 00:22:11,914 It's different, because now this matters. 413 00:22:11,914 --> 00:22:13,516 Now this matters. 414 00:22:13,516 --> 00:22:15,818 Right, and so now-- 415 00:22:15,818 --> 00:22:19,155 so now, I've got to add-- 416 00:22:19,155 --> 00:22:23,559 so it's like-- so 3 would give you trigonal planar. 417 00:22:23,559 --> 00:22:26,429 Right, 3 gives you trigonal planar, 418 00:22:26,429 --> 00:22:31,133 because I've only got those three domains, 419 00:22:31,133 --> 00:22:33,202 but now I need four. 420 00:22:33,202 --> 00:22:34,970 And there's four. 421 00:22:34,970 --> 00:22:36,739 You knew there was something else, right? 422 00:22:36,739 --> 00:22:40,042 Give more space to non-bonding domains 423 00:22:40,042 --> 00:22:43,312 and to bonding domains with higher bond order. 424 00:22:43,312 --> 00:22:45,414 That's the fourth part of the recipe. 425 00:22:45,414 --> 00:22:47,550 This just goes with what I wrote here. 426 00:22:47,550 --> 00:22:51,420 Right, so I've got differences in the molecule 427 00:22:51,420 --> 00:22:54,757 between the BPs. 428 00:22:54,757 --> 00:22:58,127 So you know now that I got to give more space 429 00:22:58,127 --> 00:23:01,230 to this double bond single bond repulsion 430 00:23:01,230 --> 00:23:03,466 than to these two single bonds. 431 00:23:03,466 --> 00:23:06,202 All right. 432 00:23:06,202 --> 00:23:14,543 So step four for this case is that the bond order 433 00:23:14,543 --> 00:23:16,479 is important. 434 00:23:19,215 --> 00:23:23,018 And this molecule will bend. 435 00:23:23,018 --> 00:23:26,856 So the shape of the molecule is going to be bent. 436 00:23:29,425 --> 00:23:31,127 It will bend, because this-- 437 00:23:31,127 --> 00:23:32,895 I didn't draw it this way. 438 00:23:32,895 --> 00:23:37,099 If I wanted to be right about it, I'm going to go like this, 439 00:23:37,099 --> 00:23:39,068 still not quite right. 440 00:23:39,068 --> 00:23:46,175 Right, and this repulsion is stronger than that repulsion. 441 00:23:46,175 --> 00:23:47,076 It bends the shape. 442 00:23:47,076 --> 00:23:50,012 So it's not trigonal planar. 443 00:23:50,012 --> 00:23:53,849 The electron domains give you a trigonal planar framework, 444 00:23:53,849 --> 00:23:55,451 but the molecule itself is bent. 445 00:23:57,987 --> 00:23:58,687 OK. 446 00:23:58,687 --> 00:24:01,290 And there's another example of that that we could do. 447 00:24:01,290 --> 00:24:06,262 There's another example of that, and that is-- let's do it here. 448 00:24:06,262 --> 00:24:09,098 And that is if we had the lone pair, which 449 00:24:09,098 --> 00:24:10,232 is what I mentioned before. 450 00:24:10,232 --> 00:24:15,838 So I'm going to take another example here, which is SO2. 451 00:24:15,838 --> 00:24:21,310 And in this case, uh-oh. 452 00:24:21,310 --> 00:24:22,845 Am I making a mistake? 453 00:24:22,845 --> 00:24:24,280 I can hear-- 454 00:24:24,280 --> 00:24:26,148 I can hear stuff. 455 00:24:26,148 --> 00:24:27,783 Did I make a mistake? 456 00:24:27,783 --> 00:24:28,317 No. 457 00:24:28,317 --> 00:24:28,984 I see this. 458 00:24:28,984 --> 00:24:31,187 I did. 459 00:24:31,187 --> 00:24:32,922 I do, and that's wrong. 460 00:24:38,494 --> 00:24:42,064 Bond order is important, but it is not under one lone pair. 461 00:24:44,700 --> 00:24:46,402 It is not under one lone pair. 462 00:24:46,402 --> 00:24:47,937 It would be under here. 463 00:24:47,937 --> 00:24:49,939 And it would be-- if there is a bond order, 464 00:24:49,939 --> 00:24:54,310 it would be best if bond order. 465 00:24:54,310 --> 00:24:55,711 Sorry about that. 466 00:24:55,711 --> 00:25:01,317 Bond O. Trigonal planar, trigonal planar, slightly bent. 467 00:25:01,317 --> 00:25:01,917 Look at this. 468 00:25:04,453 --> 00:25:05,688 I should have just kept this. 469 00:25:08,657 --> 00:25:16,398 Bent, bent, because now, I've got-- 470 00:25:16,398 --> 00:25:17,500 look at this. 471 00:25:17,500 --> 00:25:24,640 In this Lewis structure, I've got two BP and one LP. 472 00:25:24,640 --> 00:25:27,343 And finally, we have the case of the lone pair, 473 00:25:27,343 --> 00:25:30,980 and we can fill this column in, and it's bent. 474 00:25:30,980 --> 00:25:33,883 And it's bent because, again, it's the same. 475 00:25:33,883 --> 00:25:36,619 I go back to this as my key. 476 00:25:36,619 --> 00:25:39,054 OK, so I did bone pair, bond pair, 477 00:25:39,054 --> 00:25:41,290 but there was a slight shape difference 478 00:25:41,290 --> 00:25:43,559 because of the ordering of the bond pairs. 479 00:25:43,559 --> 00:25:46,829 Here, it's going to be even higher because I've 480 00:25:46,829 --> 00:25:49,198 got a lone pair. 481 00:25:49,198 --> 00:25:51,667 Actually it's a lone pair double bond, 482 00:25:51,667 --> 00:25:54,970 but it's still stronger than a bond pair bond pair repulsion. 483 00:25:54,970 --> 00:25:58,641 Lone pair bond pair, right in the middle 484 00:25:58,641 --> 00:26:01,544 is stronger than bond pair bond pair. 485 00:26:01,544 --> 00:26:03,512 That's the rank order. 486 00:26:03,512 --> 00:26:06,515 So this will be bent. 487 00:26:06,515 --> 00:26:08,984 This will be bent. 488 00:26:08,984 --> 00:26:14,423 So I've got three domains, and hold on, 489 00:26:14,423 --> 00:26:22,264 four LP more repulsive. 490 00:26:22,264 --> 00:26:28,604 Oh boy, repulsive, and so that gives me bent. 491 00:26:33,409 --> 00:26:37,746 Trigonal planar, trigonal planar, bent. 492 00:26:40,950 --> 00:26:41,717 OK. 493 00:26:41,717 --> 00:26:46,255 Did I get through that without making more mistakes? 494 00:26:46,255 --> 00:26:49,625 So we're going to go further than this, which is 495 00:26:49,625 --> 00:26:56,732 why this is only the beginning. 496 00:26:56,732 --> 00:27:00,869 But before I do, why does shape matter? 497 00:27:00,869 --> 00:27:04,139 I told you shape mattered in the very beginning, 498 00:27:04,139 --> 00:27:07,509 but why does it matter? 499 00:27:07,509 --> 00:27:10,913 Isn't it just important to know what the chemistry is 500 00:27:10,913 --> 00:27:11,981 and not the actual shape? 501 00:27:11,981 --> 00:27:13,015 Why does the shape matter? 502 00:27:13,015 --> 00:27:14,350 And so I thought I would give you 503 00:27:14,350 --> 00:27:18,187 an example of that with smell. 504 00:27:18,187 --> 00:27:21,357 And yeah, right? 505 00:27:21,357 --> 00:27:22,157 Exactly. 506 00:27:22,157 --> 00:27:24,860 And actually, I think we should do this more often. 507 00:27:24,860 --> 00:27:26,562 You know, I feel like this is inspiring. 508 00:27:26,562 --> 00:27:29,498 We talk about stopping and smelling the flowers, 509 00:27:29,498 --> 00:27:31,433 but do we actually do it? 510 00:27:31,433 --> 00:27:32,134 And look at that. 511 00:27:32,134 --> 00:27:34,670 They've got one arm around the other. 512 00:27:34,670 --> 00:27:36,438 This is a moment. 513 00:27:36,438 --> 00:27:39,808 You can't share this moment on Instagram. 514 00:27:39,808 --> 00:27:41,443 You have to put your phone down and be 515 00:27:41,443 --> 00:27:43,979 there to have this moment. 516 00:27:43,979 --> 00:27:48,283 And I highly encourage you to be inspired by this. 517 00:27:48,283 --> 00:27:51,353 Now, smell and taste are actually related. 518 00:27:51,353 --> 00:27:55,090 And smell is, you know, it's actually a fascinating thing. 519 00:27:55,090 --> 00:28:00,863 We can smell about 10,000 different smells. 520 00:28:00,863 --> 00:28:02,131 It's remarkable. 521 00:28:02,131 --> 00:28:06,502 A dog can smell between 10 and 100,000 times more. 522 00:28:06,502 --> 00:28:09,872 Right, so if you do the analogy that people do with vision, 523 00:28:09,872 --> 00:28:11,073 we can see a third of a mile. 524 00:28:11,073 --> 00:28:13,475 A dog can see about 3,000 miles. 525 00:28:13,475 --> 00:28:17,513 Right, that's pretty cool. 526 00:28:17,513 --> 00:28:19,381 But the question is why do we smell? 527 00:28:19,381 --> 00:28:20,749 How do we smell? 528 00:28:20,749 --> 00:28:22,251 How do we taste? 529 00:28:22,251 --> 00:28:25,087 And it turns out that the way that we distinguish 530 00:28:25,087 --> 00:28:27,589 from one smell and one taste and another 531 00:28:27,589 --> 00:28:29,758 has to do with the shape of the molecule. 532 00:28:29,758 --> 00:28:33,228 And so just like a key right, with a key, 533 00:28:33,228 --> 00:28:34,763 it's all of the same material. 534 00:28:34,763 --> 00:28:36,231 It's the same chemistry in the key. 535 00:28:36,231 --> 00:28:39,101 But the shape is different that can unlock the door or not. 536 00:28:39,101 --> 00:28:41,804 That is literally how our receptor cells 537 00:28:41,804 --> 00:28:44,640 work for taste and smell. 538 00:28:44,640 --> 00:28:46,542 This is a cartoon I found that I kind of like. 539 00:28:46,542 --> 00:28:51,380 See, OK, shapes, circles, squares, right. 540 00:28:51,380 --> 00:28:56,085 OK, and some shapes come in, and they make happiness, happiness, 541 00:28:56,085 --> 00:28:57,519 flowers and stuff. 542 00:28:57,519 --> 00:28:58,087 I don't know. 543 00:28:58,087 --> 00:28:58,854 Is cheese happy? 544 00:28:58,854 --> 00:29:00,055 It looks neutral. 545 00:29:00,055 --> 00:29:01,757 I would get happy with cheese. 546 00:29:01,757 --> 00:29:03,859 But anyway, fish for some reason, 547 00:29:03,859 --> 00:29:05,494 but you know, it depends. 548 00:29:05,494 --> 00:29:06,628 But it's shape dependent. 549 00:29:06,628 --> 00:29:08,497 Now the thing is, taste works that way, too. 550 00:29:08,497 --> 00:29:11,900 So this is what's happening in your tongue. 551 00:29:11,900 --> 00:29:14,203 You've got these taste buds. 552 00:29:14,203 --> 00:29:17,139 We've all heard the word taste bud, right? 553 00:29:17,139 --> 00:29:19,708 But what is really going on? 554 00:29:19,708 --> 00:29:23,645 What is really going on is a combination of chemistry 555 00:29:23,645 --> 00:29:26,815 and shape recognition. 556 00:29:26,815 --> 00:29:28,851 So the taste bud, if you look at the taste bud, 557 00:29:28,851 --> 00:29:32,488 that's inside of the little pores inside your tongue. 558 00:29:32,488 --> 00:29:33,655 There's a blow up of it. 559 00:29:33,655 --> 00:29:35,791 And so this is what the surface of your tongue looks like. 560 00:29:35,791 --> 00:29:36,959 And there's a little pore. 561 00:29:36,959 --> 00:29:38,560 And there's little filters in there 562 00:29:38,560 --> 00:29:41,063 that helps certain molecules kind of get in there. 563 00:29:41,063 --> 00:29:43,465 And what happens when they get in there. 564 00:29:43,465 --> 00:29:46,735 Well, what happens is you've got these taste receptor cells that 565 00:29:46,735 --> 00:29:48,470 are like lock key pairs. 566 00:29:48,470 --> 00:29:51,640 They actually only look at like the circle or the diamond, 567 00:29:51,640 --> 00:29:54,143 and they can tell you which one is which. 568 00:29:54,143 --> 00:29:58,080 And that's a major part of how we distinguish from one shape 569 00:29:58,080 --> 00:30:01,583 to another, and it's actually so-- 570 00:30:01,583 --> 00:30:04,052 it goes back a long way. 571 00:30:04,052 --> 00:30:04,853 Why? 572 00:30:04,853 --> 00:30:10,859 Because shape and smell are literally survival. 573 00:30:10,859 --> 00:30:12,427 They are literally like you can-- 574 00:30:12,427 --> 00:30:18,300 if you taste something, and it tastes poisonous, don't eat it. 575 00:30:18,300 --> 00:30:19,501 You live. 576 00:30:19,501 --> 00:30:21,036 Right? 577 00:30:21,036 --> 00:30:24,807 So it is a very emotional thing to smell and taste, 578 00:30:24,807 --> 00:30:28,377 because it is actually coupled to your very survival. 579 00:30:28,377 --> 00:30:32,581 And Democritus himself, Democritus, 580 00:30:32,581 --> 00:30:37,152 our friend Democritus, said that shape must be involved. 581 00:30:37,152 --> 00:30:39,888 He thought that because things that taste bitter 582 00:30:39,888 --> 00:30:43,992 are sharp that the bitter molecules were sharp. 583 00:30:43,992 --> 00:30:47,796 They must have sharpness to them, like shards of glass. 584 00:30:47,796 --> 00:30:48,764 That's how he imagined. 585 00:30:48,764 --> 00:30:50,532 And the sweet molecules were sort 586 00:30:50,532 --> 00:30:54,136 of the soft, fluffy spheres. 587 00:30:54,136 --> 00:30:57,306 That's not that far off from being sort 588 00:30:57,306 --> 00:31:01,877 of what happens a little bit. 589 00:31:01,877 --> 00:31:06,114 But when we look at it like, you know, glucose and quinine, 590 00:31:06,114 --> 00:31:09,885 we say, OK, those are very different chemistries. 591 00:31:09,885 --> 00:31:13,155 So it might not be as obvious why one of them 592 00:31:13,155 --> 00:31:15,490 taste so different than the other. 593 00:31:15,490 --> 00:31:17,826 But check out this example. 594 00:31:17,826 --> 00:31:20,863 This is the same molecule, the carvone molecule 595 00:31:20,863 --> 00:31:22,631 that is called an enantiomer, which 596 00:31:22,631 --> 00:31:24,733 means that it has handedness. 597 00:31:24,733 --> 00:31:27,302 It's the exact same chemical formula 598 00:31:27,302 --> 00:31:30,472 and the exact same structure, except for one is like this, 599 00:31:30,472 --> 00:31:32,307 and one is like that. 600 00:31:32,307 --> 00:31:33,876 That's handedness. 601 00:31:33,876 --> 00:31:34,643 Right. 602 00:31:34,643 --> 00:31:38,413 And that difference makes one of them 603 00:31:38,413 --> 00:31:40,949 taste and smell like spearmint and the other like caraway 604 00:31:40,949 --> 00:31:42,417 seeds, right? 605 00:31:42,417 --> 00:31:44,987 It's incredible. 606 00:31:44,987 --> 00:31:46,788 It means that in our tongues in our noses 607 00:31:46,788 --> 00:31:52,027 we must have chiral, the ability to determine the chirality. 608 00:31:52,027 --> 00:31:53,295 It's pretty cool. 609 00:31:53,295 --> 00:31:53,795 Right. 610 00:31:53,795 --> 00:31:56,798 So shape is critical, and this is one example of why. 611 00:31:56,798 --> 00:31:57,900 This is one example of why. 612 00:31:57,900 --> 00:31:59,835 OK. 613 00:31:59,835 --> 00:32:03,405 Back to my VSEPR recipe. 614 00:32:03,405 --> 00:32:06,808 Now, we've got to go a little further, because this 615 00:32:06,808 --> 00:32:11,213 is three electron domains, three electron domains. 616 00:32:11,213 --> 00:32:13,415 They can be messed around. 617 00:32:13,415 --> 00:32:15,150 They can be messed around. 618 00:32:15,150 --> 00:32:16,718 Right, especially in this table, we're 619 00:32:16,718 --> 00:32:19,187 talking about lone pairs or not. 620 00:32:19,187 --> 00:32:21,823 OK, I gave you the example, which I kind of fudged 621 00:32:21,823 --> 00:32:25,527 in there with bond order. 622 00:32:25,527 --> 00:32:27,596 But what happens if I go to four? 623 00:32:27,596 --> 00:32:31,333 So if I go to four, let's do an example with four-- 624 00:32:37,272 --> 00:32:41,610 if I go to four, I need some room here. 625 00:32:41,610 --> 00:32:43,879 Why don't I do it in the center here? 626 00:32:48,650 --> 00:32:52,854 Let's do an example of all possibilities 627 00:32:52,854 --> 00:32:54,723 with four, with four domains. 628 00:32:54,723 --> 00:32:56,992 And there's three really good examples, right? 629 00:32:56,992 --> 00:32:59,394 And you know them. 630 00:32:59,394 --> 00:33:03,699 Let's do CH4. 631 00:33:03,699 --> 00:33:06,902 So we'll do these kind of more quickly, CH4-- 632 00:33:06,902 --> 00:33:09,438 gesundheit-- which will be CH-- 633 00:33:12,641 --> 00:33:14,910 never leave enough room on top. 634 00:33:14,910 --> 00:33:18,080 And H. There it is. 635 00:33:18,080 --> 00:33:18,914 OK. 636 00:33:18,914 --> 00:33:20,415 Anyway. 637 00:33:20,415 --> 00:33:21,950 And NH3. 638 00:33:21,950 --> 00:33:36,431 OK, so N H H H. And H20 to all O H H. This 639 00:33:36,431 --> 00:33:38,233 is how I drew it on the first slide. 640 00:33:38,233 --> 00:33:41,703 Or this is how I drew it up there before. 641 00:33:41,703 --> 00:33:45,007 Now the thing is that in each of these cases, what 642 00:33:45,007 --> 00:33:47,642 I want you to see in these three examples is 643 00:33:47,642 --> 00:33:50,112 their similarity first. 644 00:33:50,112 --> 00:33:54,683 And their similarity is that if I pick my central atom, carbon, 645 00:33:54,683 --> 00:33:59,087 nitrogen, oxygen, if I pick my central atom, 646 00:33:59,087 --> 00:34:04,059 and I look around it, each one has four electron domains. 647 00:34:04,059 --> 00:34:04,593 Right. 648 00:34:04,593 --> 00:34:09,063 So in this sense, the kind of overarching electron geometry 649 00:34:09,063 --> 00:34:12,300 is identical for all three of those cases. 650 00:34:12,300 --> 00:34:14,902 It's identical. 651 00:34:14,902 --> 00:34:21,543 And it's tetrahedral, tetrahedral. 652 00:34:21,543 --> 00:34:25,880 OK, that's the electron pair geometry 653 00:34:25,880 --> 00:34:27,382 that's exactly the same. 654 00:34:27,382 --> 00:34:28,550 But I need to now count-- 655 00:34:31,286 --> 00:34:32,853 oh, there's the recipe. 656 00:34:32,853 --> 00:34:34,790 I need to now classify the electron pair 657 00:34:34,790 --> 00:34:36,525 as bonding or non-bonding and then 658 00:34:36,525 --> 00:34:38,860 maximize the separation between domains 659 00:34:38,860 --> 00:34:41,362 while giving more space to non-bonding domains and bonding 660 00:34:41,362 --> 00:34:45,300 domains with higher bond order as we have now talked about. 661 00:34:45,300 --> 00:34:51,806 So if I do that, here, what I have is four bonding pairs, 662 00:34:51,806 --> 00:34:55,911 zero, zero lone pairs. 663 00:34:55,911 --> 00:35:00,682 Here, I've got three bonding pairs, one lone pair. 664 00:35:00,682 --> 00:35:04,786 And now I really get to fill in stuff in my table, 665 00:35:04,786 --> 00:35:09,858 because now, I've got the examples of zero, one, 666 00:35:09,858 --> 00:35:15,330 and two lone pairs for the same electron domain cloud. 667 00:35:15,330 --> 00:35:20,769 OK, so there is zero, one, and two. 668 00:35:20,769 --> 00:35:25,607 You can see in methane, OK, the only way for this 669 00:35:25,607 --> 00:35:27,909 to maximize its repulsion, they're all the same bonding 670 00:35:27,909 --> 00:35:30,712 pair, they're all single bonds, so there's not 671 00:35:30,712 --> 00:35:32,280 going to be any kind of funny business 672 00:35:32,280 --> 00:35:36,885 of a double bond pushing harder, and there's no lone pairs. 673 00:35:36,885 --> 00:35:39,554 And so this is just going to have the tetrahedral shape. 674 00:35:39,554 --> 00:35:41,456 That will be the shape of the molecule. 675 00:35:41,456 --> 00:35:44,092 That is the electron domain shape as well. 676 00:35:44,092 --> 00:35:53,502 So in this case, it will be tetrahedral, tetrahedral. 677 00:35:53,502 --> 00:35:56,872 OK, but see, now, in this case, I've 678 00:35:56,872 --> 00:35:59,307 got three bonding pairs and one lone pair, 679 00:35:59,307 --> 00:36:03,311 and we know because of the VSEPR recipe, which has-- 680 00:36:03,311 --> 00:36:04,246 oh, it's up there. 681 00:36:04,246 --> 00:36:06,515 I keep forgetting it's up there. 682 00:36:06,515 --> 00:36:08,683 OK we know that I want to maximize the separation, 683 00:36:08,683 --> 00:36:10,685 but I got to give more space to the non-bonding, 684 00:36:10,685 --> 00:36:14,489 because the lone pair bond repulsion is stronger. 685 00:36:14,489 --> 00:36:15,323 Good. 686 00:36:15,323 --> 00:36:19,594 So what that means is it's going to be sort of like tetrahedral, 687 00:36:19,594 --> 00:36:21,363 but in one place, there is no bond. 688 00:36:21,363 --> 00:36:23,532 There's just this lone pair pushing down. 689 00:36:23,532 --> 00:36:25,634 And so the shape that you're going to get 690 00:36:25,634 --> 00:36:34,409 is called trigonal, trigonal pyramidal. 691 00:36:41,750 --> 00:36:45,353 OK, because now, that's just the way that shape looks. 692 00:36:45,353 --> 00:36:46,555 So this is going to-- 693 00:36:46,555 --> 00:36:48,924 I'll show you actually a picture of this in a second, 694 00:36:48,924 --> 00:36:50,358 OK, of what this looks like. 695 00:36:52,961 --> 00:36:55,931 And then with water, we now know that this will not 696 00:36:55,931 --> 00:36:57,832 be the most stable configuration, 697 00:36:57,832 --> 00:37:00,402 because these lone pairs are pushing on these bonds 698 00:37:00,402 --> 00:37:02,170 too much, so water is actually going 699 00:37:02,170 --> 00:37:06,875 to look like this, where these guys, the lone pairs 700 00:37:06,875 --> 00:37:10,111 can come out like that, right, that angles like that, be away 701 00:37:10,111 --> 00:37:13,481 from each other, right, and then the bonds are down there, 702 00:37:13,481 --> 00:37:17,152 and that's going to maximize the shape of the water-- 703 00:37:17,152 --> 00:37:20,288 I mean, it's going to minimize the repulsions 704 00:37:20,288 --> 00:37:22,123 that the electrons feel in the water. 705 00:37:22,123 --> 00:37:29,598 And that is back to the same name, which is bent. 706 00:37:29,598 --> 00:37:32,500 I've got a different number of electron domains, 707 00:37:32,500 --> 00:37:36,238 but I wind up with the same molecular shape. 708 00:37:36,238 --> 00:37:37,806 See that? 709 00:37:37,806 --> 00:37:39,341 Bent. 710 00:37:39,341 --> 00:37:42,510 Now, I know this is kind of small. 711 00:37:42,510 --> 00:37:45,847 I've got tables that have all this at the end 712 00:37:45,847 --> 00:37:47,115 that you'll have in the slides. 713 00:37:47,115 --> 00:37:50,552 OK, so I know this is a little bit crammed in here, 714 00:37:50,552 --> 00:37:52,287 but the process of writing this is 715 00:37:52,287 --> 00:37:56,324 very, very fun and fulfilling. 716 00:37:56,324 --> 00:37:58,526 Now, we can keep going. 717 00:37:58,526 --> 00:38:00,729 But I want to tell you about a labeling system that's 718 00:38:00,729 --> 00:38:02,564 actually really helpful. 719 00:38:02,564 --> 00:38:06,901 So if we keep going, we kind of want 720 00:38:06,901 --> 00:38:09,404 a system to be able to think about these things. 721 00:38:09,404 --> 00:38:11,606 And so there is a system. 722 00:38:11,606 --> 00:38:12,941 Again, this is chemistry. 723 00:38:12,941 --> 00:38:14,509 We know how to name things. 724 00:38:14,509 --> 00:38:16,611 Oh, but I promised you I'd show you that first. 725 00:38:16,611 --> 00:38:17,646 So here it is. 726 00:38:17,646 --> 00:38:18,146 There it is. 727 00:38:18,146 --> 00:38:18,913 I didn't know why. 728 00:38:18,913 --> 00:38:20,015 I click to that already. 729 00:38:20,015 --> 00:38:21,816 That's this. 730 00:38:21,816 --> 00:38:25,153 And the reason I wanted to show you this, this is from 731 00:38:25,153 --> 00:38:26,888 [? Avril, ?] your textbook that you're all 732 00:38:26,888 --> 00:38:28,556 reading so carefully. 733 00:38:28,556 --> 00:38:30,091 And look at that. 734 00:38:30,091 --> 00:38:32,594 This really brings it home. 735 00:38:32,594 --> 00:38:34,062 Look at that lone pair. 736 00:38:34,062 --> 00:38:36,264 Now you're seeing it as the electrons 737 00:38:36,264 --> 00:38:41,036 feel it, which is a probability distribution cloud. 738 00:38:41,036 --> 00:38:42,437 That's the lone pair, and now you 739 00:38:42,437 --> 00:38:45,006 can see the lone pair wants space. 740 00:38:45,006 --> 00:38:48,977 It wants room, and it's pushing down 741 00:38:48,977 --> 00:38:54,149 on these bonds, which are pushing away from each other. 742 00:38:54,149 --> 00:38:55,517 And that's how you can figure out 743 00:38:55,517 --> 00:38:58,853 what shape it is, trigonal pyramidal. 744 00:38:58,853 --> 00:39:03,558 That's trigonal pyramidal, OK, the molecule. 745 00:39:07,362 --> 00:39:10,398 Right, as I said, we need a way to label things in chemistry. 746 00:39:10,398 --> 00:39:13,401 So we can keep going-- linear, trigonal planar, tetrahedral, 747 00:39:13,401 --> 00:39:19,841 trigonal bipyramidal, oh, five, octahedral, six. 748 00:39:19,841 --> 00:39:23,878 Don't get confused octa, eight, but octahedral 749 00:39:23,878 --> 00:39:28,950 is for six electron pair domains, right. 750 00:39:28,950 --> 00:39:30,385 But we need a system to name this. 751 00:39:30,385 --> 00:39:33,988 And so the chemists have brilliantly come up with AXE. 752 00:39:33,988 --> 00:39:36,458 Now A is the central atom. 753 00:39:36,458 --> 00:39:40,261 X is the bonding pair regions, and E is the lone pair regions. 754 00:39:43,131 --> 00:39:48,636 X and E. OK, and so if I go back to like BF3, 755 00:39:48,636 --> 00:39:50,305 well, this would be-- 756 00:39:50,305 --> 00:39:52,741 oh there you go, AX3. 757 00:39:52,741 --> 00:39:56,644 I say, what is the shape of AX3? 758 00:39:56,644 --> 00:39:58,213 I know I've got to central atom, A, 759 00:39:58,213 --> 00:40:01,950 and I've got three bonding pairs around it and no lone pairs. 760 00:40:01,950 --> 00:40:04,419 That's what that means. 761 00:40:04,419 --> 00:40:06,721 I could go back as SO2. 762 00:40:06,721 --> 00:40:08,256 Where is SO2? 763 00:40:08,256 --> 00:40:09,224 Did I erase it? 764 00:40:09,224 --> 00:40:10,358 Maybe I erased SO2. 765 00:40:17,565 --> 00:40:18,867 I did erase SO2. 766 00:40:22,537 --> 00:40:26,941 Oh, I didn't erase SO2. 767 00:40:26,941 --> 00:40:28,143 Happiness. 768 00:40:28,143 --> 00:40:28,910 Look at this. 769 00:40:28,910 --> 00:40:30,044 SO2 would be AX2E. 770 00:40:32,814 --> 00:40:36,317 Or if you want, you can put a 1 there. 771 00:40:36,317 --> 00:40:40,588 It's a highly sophisticated, advanced labeling system. 772 00:40:40,588 --> 00:40:43,391 That simply allows us to keep going, 773 00:40:43,391 --> 00:40:45,960 to keep going without writing so many words. 774 00:40:45,960 --> 00:40:48,229 But we know now, A is the central atom. 775 00:40:48,229 --> 00:40:49,998 X is the number of bonding pair regions. 776 00:40:49,998 --> 00:40:51,833 E is the number of lone pair regions. 777 00:40:51,833 --> 00:40:54,235 And we know about our rules, and we know about bond order. 778 00:40:56,604 --> 00:41:00,575 So now if I look at those same-- 779 00:41:00,575 --> 00:41:01,876 really? 780 00:41:01,876 --> 00:41:04,879 What happened to-- oh, there they are up there. 781 00:41:04,879 --> 00:41:07,081 If I look at those same ones, well, OK, 782 00:41:07,081 --> 00:41:09,951 look those are tetrahedral. 783 00:41:09,951 --> 00:41:13,087 OK, the electron pair distribution 784 00:41:13,087 --> 00:41:17,192 is tetrahedral, but-- gesundheit. 785 00:41:17,192 --> 00:41:19,561 But as you can see in these pictures, 786 00:41:19,561 --> 00:41:22,897 you can get three different molecular shapes. 787 00:41:22,897 --> 00:41:26,000 You can get tetrahedral, same as the electron pair. 788 00:41:26,000 --> 00:41:29,137 You can get trigonal pyramidal, or you can get bent. 789 00:41:29,137 --> 00:41:32,373 Those are the names of the molecule. 790 00:41:32,373 --> 00:41:34,008 Notice that those aren't the names that 791 00:41:34,008 --> 00:41:35,343 include the lone pairs. 792 00:41:35,343 --> 00:41:38,146 Lone pairs are how you find which one of these categories 793 00:41:38,146 --> 00:41:40,215 you're in. 794 00:41:40,215 --> 00:41:41,916 But those are the names of the molecules. 795 00:41:41,916 --> 00:41:43,284 Those are really important, those 796 00:41:43,284 --> 00:41:45,687 names of the molecular shape. 797 00:41:45,687 --> 00:41:48,056 Now, if I move over one-- 798 00:41:48,056 --> 00:41:50,892 OK, oh there they are, names, tetrahedral, trigonal, 799 00:41:50,892 --> 00:41:52,026 pyramidal, bent. 800 00:41:52,026 --> 00:41:53,094 Now, let's move over one. 801 00:41:53,094 --> 00:41:54,162 So now I'm going to stop. 802 00:41:54,162 --> 00:41:57,832 I'm not going to keep on writing everything down. 803 00:41:57,832 --> 00:41:58,967 Let's see one last example. 804 00:41:58,967 --> 00:42:01,102 So here's trigonal bipyramidal. 805 00:42:01,102 --> 00:42:04,472 This is what happens when you have five electron pair 806 00:42:04,472 --> 00:42:06,474 domains. 807 00:42:06,474 --> 00:42:08,343 Again, and I keep saying this, but I 808 00:42:08,343 --> 00:42:10,778 know that this can lead to confusion later. 809 00:42:10,778 --> 00:42:15,850 So I keep on reiterating, the electron payer domain 810 00:42:15,850 --> 00:42:19,921 count, right, the five here, the five here, which gives us 811 00:42:19,921 --> 00:42:23,691 this overall kind of electron payer domain shape, that 812 00:42:23,691 --> 00:42:27,362 would be five there, right, trigonal bipyramidal, 813 00:42:27,362 --> 00:42:33,268 that includes a single, double, or triple bond is a domain. 814 00:42:33,268 --> 00:42:35,837 It's a BP. 815 00:42:35,837 --> 00:42:38,273 Right, it's a BP domain. 816 00:42:38,273 --> 00:42:40,408 A lone pair is a domain. 817 00:42:40,408 --> 00:42:43,645 How many of those do you have floating around your molecule, 818 00:42:43,645 --> 00:42:44,746 around your atom? 819 00:42:44,746 --> 00:42:46,981 Sorry, your central atom. 820 00:42:46,981 --> 00:42:49,484 And then you go down and you sort of decompose it 821 00:42:49,484 --> 00:42:54,289 in terms of how many of them are bonding pairs, X's, versus how 822 00:42:54,289 --> 00:42:55,557 many of them are lone pairs. 823 00:42:55,557 --> 00:42:59,327 So let's do one last example. 824 00:43:02,063 --> 00:43:03,898 And it'll be for five. 825 00:43:03,898 --> 00:43:06,434 It'll be for five, right, so five. 826 00:43:12,607 --> 00:43:14,776 And I want you to really-- 827 00:43:14,776 --> 00:43:16,177 I'll go with the center again. 828 00:43:16,177 --> 00:43:19,614 I want you to really kind of get a feeling for why this works. 829 00:43:19,614 --> 00:43:21,149 And this is, I think, a nice example. 830 00:43:24,152 --> 00:43:33,895 If you had the molecule, if you had the molecule SF4, 831 00:43:33,895 --> 00:43:35,630 I'll give you two examples today that 832 00:43:35,630 --> 00:43:40,301 violate the octet rule, right, because chemistry 833 00:43:40,301 --> 00:43:42,303 lives in the fast lane. 834 00:43:42,303 --> 00:43:49,344 If you have SF4, S is willing to have an expanded octet, 835 00:43:49,344 --> 00:43:50,678 all right. 836 00:43:50,678 --> 00:43:52,714 As you go down in the periodic table, 837 00:43:52,714 --> 00:43:56,751 atoms are more willing to live in the fast lane 838 00:43:56,751 --> 00:43:58,353 and break the rules. 839 00:43:58,353 --> 00:44:05,827 S-- we've drawn it like this, F, F, F, all right, 840 00:44:05,827 --> 00:44:08,029 we've drawn it like this, violating 841 00:44:08,029 --> 00:44:09,664 the octet rule and all that, but still 842 00:44:09,664 --> 00:44:12,266 being happy because it's lowest in energy. 843 00:44:12,266 --> 00:44:17,305 And these are all my electron non-binding domains. 844 00:44:22,510 --> 00:44:25,013 OK. 845 00:44:25,013 --> 00:44:27,849 If I count-- remember, those aren't going to matter. 846 00:44:27,849 --> 00:44:28,783 They're on the outside. 847 00:44:28,783 --> 00:44:30,318 I'm picking one atom. 848 00:44:30,318 --> 00:44:35,490 A is S. Right, A is S in this case. 849 00:44:35,490 --> 00:44:38,826 And in this case, I've got-- 850 00:44:38,826 --> 00:44:41,095 you know, I've got, OK, how many body pairs? 851 00:44:41,095 --> 00:44:47,669 I've got four bonding pairs and one lone pair, 852 00:44:47,669 --> 00:44:49,504 and one lone pair. 853 00:44:49,504 --> 00:44:50,905 And so you can see-- 854 00:44:50,905 --> 00:44:55,710 I can just look this up here AX4E1. 855 00:44:55,710 --> 00:44:57,412 It must be a seesaw structure. 856 00:44:57,412 --> 00:44:59,547 But I want you to see it, and this 857 00:44:59,547 --> 00:45:04,519 is where playing with these models really helps you see it. 858 00:45:04,519 --> 00:45:11,459 Because if you think about this, it seems, at first, 859 00:45:11,459 --> 00:45:15,496 that if I had four bonding pairs and one lone pair, 860 00:45:15,496 --> 00:45:17,732 why can't I just write it like this? 861 00:45:17,732 --> 00:45:21,402 This seems like a good idea at first, right? 862 00:45:21,402 --> 00:45:25,707 S, and then you've got a fluorine down here. 863 00:45:25,707 --> 00:45:28,176 And then you're going to go out. 864 00:45:28,176 --> 00:45:32,513 I'm using a kind of cool new notation here. 865 00:45:32,513 --> 00:45:34,415 Right-- and then you're going to go. 866 00:45:34,415 --> 00:45:36,017 Did somebody just say whoa? 867 00:45:36,017 --> 00:45:37,685 Or is that just in my mind? 868 00:45:37,685 --> 00:45:40,455 Like that, but I'm saying whoa. 869 00:45:40,455 --> 00:45:43,024 That's a terrible rendition of this notation. 870 00:45:43,024 --> 00:45:49,197 But this means-- now I've got to come on the board. 871 00:45:49,197 --> 00:45:51,099 And for me, that's challenging because I'm not 872 00:45:51,099 --> 00:45:53,968 very good at drawing 3D things. 873 00:45:53,968 --> 00:45:58,873 And so we use these little shaded in kind of sticks 874 00:45:58,873 --> 00:46:00,942 like that, and it comes out of the board, 875 00:46:00,942 --> 00:46:02,443 and then that's like the dashed one, 876 00:46:02,443 --> 00:46:03,544 and it goes into the board. 877 00:46:07,148 --> 00:46:09,050 So there's one-- that looks terrible. 878 00:46:12,220 --> 00:46:13,488 I'm going to try one more time. 879 00:46:13,488 --> 00:46:20,194 So maybe if I just do this, F, F. And this 880 00:46:20,194 --> 00:46:22,163 is in the same plane here. 881 00:46:22,163 --> 00:46:24,599 These three are in a plane, and that's going down. 882 00:46:24,599 --> 00:46:27,935 And you've got your lone pair up here. 883 00:46:27,935 --> 00:46:30,304 That looks pretty good. 884 00:46:30,304 --> 00:46:36,844 Why is that better than something like this? 885 00:46:36,844 --> 00:46:42,283 And now, one coming out of the board and the other going 886 00:46:42,283 --> 00:46:46,954 into the board, all right, and now this would be-- gesundheit. 887 00:46:46,954 --> 00:46:49,724 This would be my other possibility. 888 00:46:49,724 --> 00:46:51,092 I mean, if I think about, I think 889 00:46:51,092 --> 00:46:52,393 why can't it just be this? 890 00:46:52,393 --> 00:46:53,494 These look-- I don't know. 891 00:46:53,494 --> 00:46:55,096 These look nice and spread out. 892 00:46:55,096 --> 00:46:58,032 Why not? 893 00:46:58,032 --> 00:47:00,334 It's the lone pair again. 894 00:47:00,334 --> 00:47:02,336 It's the lone pair. 895 00:47:02,336 --> 00:47:03,771 It's got to be, because, you know, 896 00:47:03,771 --> 00:47:09,944 I put up there, somewhere, there's not there, 897 00:47:09,944 --> 00:47:13,781 that the lone pair repels the bonds more, 898 00:47:13,781 --> 00:47:18,119 and I've got more than say a bond and a bond. 899 00:47:18,119 --> 00:47:21,789 But the point is I've got three of those here. 900 00:47:21,789 --> 00:47:27,895 This has three, one, two, and three. 901 00:47:27,895 --> 00:47:29,697 This has two. 902 00:47:29,697 --> 00:47:32,400 This is a happier structure. 903 00:47:32,400 --> 00:47:33,467 Right. 904 00:47:33,467 --> 00:47:36,470 So I wanted you to see-- so this is the way to think about it. 905 00:47:36,470 --> 00:47:38,072 You're using VSEPR. 906 00:47:38,072 --> 00:47:41,876 You're applying these principles. 907 00:47:41,876 --> 00:47:44,712 I mean, it's just a four-point recipe, 908 00:47:44,712 --> 00:47:46,914 but I'm hoping that in thinking about it this way 909 00:47:46,914 --> 00:47:48,916 and having the little models in your hand, 910 00:47:48,916 --> 00:47:51,953 which you have in this goody bag, 911 00:47:51,953 --> 00:47:56,557 that you guys will also kind of have a feeling for it, 912 00:47:56,557 --> 00:47:58,559 so that yes, you have the tables that 913 00:47:58,559 --> 00:48:02,363 are written out much better than how I wrote them out. 914 00:48:02,363 --> 00:48:04,966 And here's one in the lecture notes that I'll leave you, 915 00:48:04,966 --> 00:48:06,801 right, total domains. 916 00:48:06,801 --> 00:48:12,540 It's very similar, notation, structures, OK, shapes. 917 00:48:12,540 --> 00:48:17,211 But also that you have a feeling for why this is the case. 918 00:48:17,211 --> 00:48:19,680 All right, shapes of molecules. 919 00:48:19,680 --> 00:48:25,620 See you guys on Wednesday-- no, Friday.