1 00:00:16,515 --> 00:00:20,419 But back to MO Theory, which is where what we 2 00:00:20,419 --> 00:00:23,522 talked about last Friday. 3 00:00:23,522 --> 00:00:25,124 And there are sort of two last things 4 00:00:25,124 --> 00:00:28,694 I wanted to mention now related to MO Theory 5 00:00:28,694 --> 00:00:31,530 before moving on to the topic of hybridization. 6 00:00:34,333 --> 00:00:36,969 Now, before I do that, you know, I'm going to use a couple 7 00:00:36,969 --> 00:00:38,004 of videos today and I'm-- 8 00:00:38,004 --> 00:00:39,438 I'm not going to show you this one, 9 00:00:39,438 --> 00:00:41,040 but I just want to mention there's 10 00:00:41,040 --> 00:00:43,542 lots of videos that help, you know, 11 00:00:43,542 --> 00:00:45,144 animate this stuff, right? 12 00:00:45,144 --> 00:00:48,414 So like this is what-- so like-- 13 00:00:48,881 --> 00:00:50,182 Oh, OK. 14 00:00:50,182 --> 00:00:53,085 [VIDEO PLAYBACK] 15 00:00:53,085 --> 00:00:54,453 Bonding molecular orbital. 16 00:00:58,290 --> 00:00:58,824 [END PLAYBACK] 17 00:00:58,824 --> 00:01:01,360 Antibonding, we talked about this last Friday. 18 00:01:01,360 --> 00:01:04,263 But look at this animation. 19 00:01:04,263 --> 00:01:06,832 I couldn't do that on the board. 20 00:01:06,832 --> 00:01:07,299 Watch this. 21 00:01:07,299 --> 00:01:07,833 [VIDEO PLAYBACK] 22 00:01:07,833 --> 00:01:09,301 Antibonding molecular orbital formed 23 00:01:09,301 --> 00:01:11,804 by the combination of two 1s orbitals 24 00:01:11,804 --> 00:01:16,809 are called sigma 1s and sigma star 1s respectively. 25 00:01:16,809 --> 00:01:17,376 [END PLAYBACK] 26 00:01:17,376 --> 00:01:19,478 Kind of remembering stuff now, right, from Friday? 27 00:01:19,478 --> 00:01:20,112 [VIDEO PLAYBACK] 28 00:01:20,112 --> 00:01:21,213 The bonding molecular-- 29 00:01:21,213 --> 00:01:22,214 Oh, look at that. 30 00:01:22,214 --> 00:01:26,318 -- is lower in energy than the original [INAUDIBLE].. 31 00:01:26,318 --> 00:01:26,952 [END PLAYBACK] 32 00:01:26,952 --> 00:01:29,488 That's that kind of animation that you just can't-- you know, 33 00:01:29,488 --> 00:01:31,323 I can't animate the bonding and antibonding. 34 00:01:31,323 --> 00:01:33,759 Well, I kind of can with my hands, but there it is. 35 00:01:33,759 --> 00:01:35,860 And there's lots and lots of those kinds of videos. 36 00:01:35,860 --> 00:01:38,130 I'll show you a couple today related to hybridization, 37 00:01:38,130 --> 00:01:40,699 because it really does help see these 3D 38 00:01:40,699 --> 00:01:43,569 orbitals, right, in their full shape and what's happening. 39 00:01:43,569 --> 00:01:45,670 So I highly recommend it, especially if you're 40 00:01:45,670 --> 00:01:49,708 having some conceptual questions related to stuff 41 00:01:49,708 --> 00:01:51,477 we talked about Friday and today. 42 00:01:51,477 --> 00:01:53,612 Take a look at some of those videos. 43 00:01:53,612 --> 00:01:57,683 Now, where we left off on Friday, 44 00:01:57,683 --> 00:02:00,419 before I get to nitrous nitric oxide, which 45 00:02:00,419 --> 00:02:05,091 has all those different uses in the world, and many more. 46 00:02:05,091 --> 00:02:08,160 We left off with the homonuclear dimers. 47 00:02:08,160 --> 00:02:10,062 That's what we were doing on Friday, right? 48 00:02:10,062 --> 00:02:12,631 How do the atomic orbitals come together 49 00:02:12,631 --> 00:02:16,802 to make orbitals that are molecular MOs, right? 50 00:02:16,802 --> 00:02:20,706 And we did it for dimers that have the same atom, right? 51 00:02:20,706 --> 00:02:24,877 And so here-- so we did nitrogen and 2 and we did O2, right? 52 00:02:24,877 --> 00:02:26,278 And so let's do that on the board 53 00:02:26,278 --> 00:02:27,980 and that-- because now we're going 54 00:02:27,980 --> 00:02:32,551 to start with one that has N and O, heteronuclear dimer, right? 55 00:02:32,551 --> 00:02:33,986 Two different atoms. 56 00:02:33,986 --> 00:02:35,821 But if I had the same one, remember, 57 00:02:35,821 --> 00:02:37,456 this is what it would look like, right? 58 00:02:37,456 --> 00:02:40,292 So here-- here would be, say, N2. 59 00:02:40,292 --> 00:02:43,395 Would-- you know, I'm going to just stick with the valence. 60 00:02:43,395 --> 00:02:52,571 So the 2s for our nitrogen atom, and the 2p would have, 61 00:02:52,571 --> 00:02:54,540 remember, Hund's rule. 62 00:02:54,540 --> 00:02:55,207 All right. 63 00:02:55,207 --> 00:02:56,041 OK. 64 00:02:56,041 --> 00:02:57,676 So that's what the 2p would look like. 65 00:02:57,676 --> 00:03:01,780 And then over here, we would have the other atom. 66 00:03:01,780 --> 00:03:05,050 This is how we roll when we talk about MOs. 67 00:03:05,050 --> 00:03:07,386 And we'd have the 2s over here. 68 00:03:07,386 --> 00:03:09,288 And this is how we start. 69 00:03:09,288 --> 00:03:11,323 These are my AOs for the 2 nitrogen atoms. 70 00:03:11,323 --> 00:03:11,790 Right. 71 00:03:11,790 --> 00:03:14,426 This is what we did, we're just getting back in the mood 72 00:03:14,426 --> 00:03:15,794 because we had the long weekend. 73 00:03:15,794 --> 00:03:17,496 And when we make the MOs, remember, 74 00:03:17,496 --> 00:03:19,431 we have all those sort of things that we talked 75 00:03:19,431 --> 00:03:22,768 about in terms of how these-- 76 00:03:22,768 --> 00:03:26,438 this difference between the bonding and the antibonding 77 00:03:26,438 --> 00:03:31,076 orbital, right, is related to the overlap 78 00:03:31,076 --> 00:03:34,079 in the same symmetry of the two AOs that come together. 79 00:03:34,079 --> 00:03:35,447 [INAUDIBLE] we talked about that, 80 00:03:35,447 --> 00:03:37,349 the more overlap, the biggest this delta. 81 00:03:37,349 --> 00:03:38,317 Gesundheit. 82 00:03:38,317 --> 00:03:39,084 All right. 83 00:03:39,084 --> 00:03:41,520 And then we also-- so that would be filled, 84 00:03:41,520 --> 00:03:43,055 this would be filled, right? 85 00:03:43,055 --> 00:03:48,427 Sigma 2 s, sigma a. 86 00:03:48,427 --> 00:03:52,264 Sigma star 2s, right? 87 00:03:52,264 --> 00:03:55,466 And then for nitrogen, we also talked about how-- 88 00:03:55,466 --> 00:03:58,470 oh, boy, these are reversed, right? 89 00:03:58,470 --> 00:04:00,773 See, I'm now already... 90 00:04:00,806 --> 00:04:01,907 ...backwards twice, 91 00:04:01,907 --> 00:04:03,442 which is not what I want. 92 00:04:03,442 --> 00:04:05,911 OK. 93 00:04:05,911 --> 00:04:09,381 And this was-- but this is the weird thing about nitrogen, 94 00:04:09,381 --> 00:04:14,386 because if we go to oxygen, then the way it goes is, you know, 95 00:04:14,386 --> 00:04:17,389 you've got your 2s in oxygen. OK. 96 00:04:17,389 --> 00:04:25,831 And in oxygen, you've got your 6 valence electrons in the 2p. 97 00:04:25,831 --> 00:04:30,869 And over here, you've also got the same. 98 00:04:30,869 --> 00:04:31,570 OK. 99 00:04:31,570 --> 00:04:33,572 And you've also got that 2s. 100 00:04:33,572 --> 00:04:35,107 And-- but for oxygen-- 101 00:04:38,777 --> 00:04:39,311 OK. 102 00:04:39,311 --> 00:04:41,380 So those are the sigma, sigma star. 103 00:04:41,380 --> 00:04:51,223 But for oxygen, we go to the ordering that we usually have, 104 00:04:51,223 --> 00:04:56,328 which is that-- remember, those pi orbitals have-- 105 00:04:56,328 --> 00:04:58,597 and this isn't necessarily on a scale. 106 00:04:58,597 --> 00:05:00,032 But those pi orbitals-- all right. 107 00:05:00,032 --> 00:05:04,903 So this was sigma, sigma star, and these are the pi orbitals. 108 00:05:04,903 --> 00:05:07,806 Pi and pi star, right? 109 00:05:10,776 --> 00:05:13,178 Sigma p. 110 00:05:13,178 --> 00:05:14,346 Sigma p. 111 00:05:14,346 --> 00:05:14,913 All right. 112 00:05:14,913 --> 00:05:18,517 2p, 2s, sigma. 113 00:05:18,517 --> 00:05:23,355 This would be sigma s, sigma 2s, sigma 2s star, sigma 2p, 114 00:05:23,355 --> 00:05:24,990 if you want to be exact about it. 115 00:05:24,990 --> 00:05:26,992 Sigma 2p star. 116 00:05:26,992 --> 00:05:30,462 Pi x, pi y, pi x star, pi y start. 117 00:05:30,462 --> 00:05:31,997 We talked about all this on Friday, 118 00:05:31,997 --> 00:05:34,266 I'm just getting us back in the mood. 119 00:05:34,266 --> 00:05:36,835 But the way we left off was that these are-- 120 00:05:36,835 --> 00:05:37,369 OK. 121 00:05:37,369 --> 00:05:40,005 So for-- if I fill these all up now-- 122 00:05:40,005 --> 00:05:40,472 right. 123 00:05:40,472 --> 00:05:42,641 Remember, we do the MO filling, then we'd 124 00:05:42,641 --> 00:05:46,078 have this, and this, and-- 125 00:05:46,078 --> 00:05:47,446 ooh. 126 00:05:47,446 --> 00:05:48,480 Now, hold on. 127 00:05:48,480 --> 00:05:49,214 Yep. 128 00:05:49,214 --> 00:05:55,020 This and there and there for oxygen. And then 129 00:05:55,020 --> 00:05:56,922 over here we're filling them up. 130 00:05:56,922 --> 00:05:59,024 We got-- those are filled, those are filled, 131 00:05:59,024 --> 00:06:01,493 and this is filled for nitrogen. Remember, 132 00:06:01,493 --> 00:06:03,228 I showed the movie pouring liquid oxygen, 133 00:06:03,228 --> 00:06:08,233 pouring liquid nitrogen. Oxygen has unpaired electrons, 134 00:06:08,233 --> 00:06:10,369 which means it's paramagnetic. 135 00:06:10,369 --> 00:06:11,036 It has unpaired. 136 00:06:11,036 --> 00:06:13,672 Electrons, the O2 dimer. 137 00:06:13,672 --> 00:06:14,473 This is O2. 138 00:06:14,473 --> 00:06:15,774 These are the MOs of O2. 139 00:06:15,774 --> 00:06:17,309 These are the atoms. 140 00:06:17,309 --> 00:06:18,977 These are the MOs of N2. 141 00:06:18,977 --> 00:06:21,213 N2 doesn't have any unpaired electrons 142 00:06:21,213 --> 00:06:22,748 so it's not paramagnetic. 143 00:06:22,748 --> 00:06:25,150 But the thing that we left off on-- that's what I'm saying 144 00:06:25,150 --> 00:06:34,626 is, that these two switch order for those dimers, 145 00:06:34,626 --> 00:06:39,131 for lithium through nitrogen. Those two switch. 146 00:06:39,131 --> 00:06:39,631 All right. 147 00:06:39,631 --> 00:06:40,899 We talked about that on Friday. 148 00:06:40,899 --> 00:06:47,339 The reason is because for those atoms, these sigma-- 149 00:06:47,339 --> 00:06:55,781 these sigma p orbitals can mix in with the sigma s orbitals. 150 00:06:55,781 --> 00:06:57,383 And so you get more. 151 00:06:57,383 --> 00:06:59,451 Because, remember, the more overlap, 152 00:06:59,451 --> 00:07:01,553 the greater the energy, rate? 153 00:07:01,553 --> 00:07:04,289 The greater that delta between bonding and antibonding, right? 154 00:07:04,289 --> 00:07:08,660 So the more mixing you have, the more spread you get. 155 00:07:08,660 --> 00:07:12,030 And it's so much that for those dimers you push the orbital up. 156 00:07:12,030 --> 00:07:12,564 OK. 157 00:07:12,564 --> 00:07:15,167 That's all what we talked about Friday. 158 00:07:15,167 --> 00:07:16,802 Now, I got on of each. 159 00:07:16,802 --> 00:07:22,207 I got one of these on the board so that you can see them 160 00:07:22,207 --> 00:07:25,477 as we now take one atom from one side and one from the other. 161 00:07:25,477 --> 00:07:28,847 It's actually kind of what you expect. 162 00:07:28,847 --> 00:07:30,849 You just have to have one thing in mind 163 00:07:30,849 --> 00:07:33,018 when you think about No-- 164 00:07:33,018 --> 00:07:37,589 so if this is N, OK, over here, and we're 165 00:07:37,589 --> 00:07:43,128 going to put 2s there and 2p there. 166 00:07:43,128 --> 00:07:46,698 Here, here, here, here. 167 00:07:46,698 --> 00:07:48,033 There's my N atom. 168 00:07:48,033 --> 00:07:50,869 And now I've got O over here. 169 00:07:50,869 --> 00:07:52,070 So I've got my-- 170 00:07:52,070 --> 00:07:55,574 but, now, see, the thing is always more electronegative. 171 00:07:55,574 --> 00:07:59,711 And the way this works for a heteronuclear dimer is-- 172 00:07:59,711 --> 00:08:01,447 let's write this on the board. 173 00:08:01,447 --> 00:08:07,519 So for a heteronuclear, that means that the two atoms 174 00:08:07,519 --> 00:08:08,520 are different. 175 00:08:08,520 --> 00:08:09,221 OK. 176 00:08:09,221 --> 00:08:21,366 But for a heteronuclear dimer, the bonding MOs 177 00:08:21,366 --> 00:08:32,277 are closer in energy to the more electronegative atom. 178 00:08:32,277 --> 00:08:35,713 Electroneg atom. 179 00:08:40,118 --> 00:08:41,620 Atom. 180 00:08:41,620 --> 00:08:43,922 So what that means is that if I draw-- 181 00:08:43,922 --> 00:08:45,757 so if I draw my oxygen levels-- 182 00:08:45,757 --> 00:08:46,892 but you know this, right? 183 00:08:46,892 --> 00:08:49,928 You know this, also, from all the work 184 00:08:49,928 --> 00:08:52,564 we did on atoms, right? 185 00:08:52,564 --> 00:08:54,933 You know a little something about-- remember, 186 00:08:54,933 --> 00:08:57,503 this axis is energy. 187 00:08:57,503 --> 00:08:59,938 This axis is energy. 188 00:08:59,938 --> 00:09:04,009 And so if this is 2s for oxygen, and then the 2p's are 189 00:09:04,009 --> 00:09:07,012 going to be sort of like here. 190 00:09:07,012 --> 00:09:07,513 OK. 191 00:09:10,148 --> 00:09:12,518 And we'll fill them up thinking about Hund's rule. 192 00:09:12,518 --> 00:09:16,121 Well, now, what we're going to have is that those-- 193 00:09:16,121 --> 00:09:23,128 the MOs for the No molecule are going to come closer, 194 00:09:23,128 --> 00:09:26,965 they're going to come further down from that side, right? 195 00:09:26,965 --> 00:09:28,700 Then they come from that side. 196 00:09:28,700 --> 00:09:29,334 Do you see that? 197 00:09:29,334 --> 00:09:31,069 There's an asymmetry. 198 00:09:31,069 --> 00:09:32,938 I made it kind of subtle. 199 00:09:32,938 --> 00:09:35,440 I made it kind-- and why is this curved? 200 00:09:35,440 --> 00:09:36,875 That's not good. 201 00:09:36,875 --> 00:09:38,310 What's going on here? 202 00:09:38,310 --> 00:09:42,781 There's a little bit of an asymmetry here, right? 203 00:09:42,781 --> 00:09:47,553 So-- so this is lower down-- 204 00:09:47,553 --> 00:09:48,987 these are lower down, right? 205 00:09:48,987 --> 00:09:52,891 So when you draw your orbitals now-- 206 00:09:52,891 --> 00:09:54,893 oh, man. 207 00:09:54,893 --> 00:09:58,830 I'm going to draw this a little bit lower. 208 00:09:58,830 --> 00:10:01,166 Right. 209 00:10:01,166 --> 00:10:04,536 So now when you draw then, you see that bonding orbital 210 00:10:04,536 --> 00:10:07,072 is going to be closer. 211 00:10:07,072 --> 00:10:09,341 You see, this is a bonding orbital still. 212 00:10:09,341 --> 00:10:10,642 It's still bonding, right? 213 00:10:10,642 --> 00:10:14,379 It's going to be a sigma p, sigma 2p. 214 00:10:14,379 --> 00:10:17,482 But it's closer in energy to the more electronegative levels. 215 00:10:17,482 --> 00:10:18,016 You see that? 216 00:10:18,016 --> 00:10:18,550 Right. 217 00:10:18,550 --> 00:10:21,620 So it's not symmetric anymore. 218 00:10:21,620 --> 00:10:22,988 OK. 219 00:10:22,988 --> 00:10:26,224 And then the same what happened with these guys, right, 220 00:10:26,224 --> 00:10:31,663 they'd be closer in energy to the-- 221 00:10:31,663 --> 00:10:33,298 yeah. 222 00:10:33,298 --> 00:10:34,665 They would be closer. 223 00:10:34,665 --> 00:10:37,302 And I'm not leaving myself enough room here. 224 00:10:37,302 --> 00:10:38,770 That's why I've got some videos. 225 00:10:38,770 --> 00:10:40,238 They do it better. 226 00:10:40,238 --> 00:10:42,874 All right. 227 00:10:42,874 --> 00:10:43,408 OK. 228 00:10:43,408 --> 00:10:45,310 We'll leave that one there. 229 00:10:45,310 --> 00:10:47,613 It's a little bit better. 230 00:10:47,613 --> 00:10:50,682 Not much, but a little bit. 231 00:10:50,682 --> 00:10:54,252 So the bite-- now-- oh, by the way, for No-- 232 00:10:54,252 --> 00:10:56,321 let's talk about MO for a second, because there's 233 00:10:56,321 --> 00:10:59,424 another thing that's important that we talk about, 234 00:10:59,424 --> 00:11:04,129 which is bond order, and, you know, the bond-- 235 00:11:04,129 --> 00:11:06,765 oh, electron configuration is another thing, right? 236 00:11:06,765 --> 00:11:13,271 So like the configuration, we can write this out, right? 237 00:11:13,271 --> 00:11:17,909 So the configuration of, say, 02 would be sigma 2s, right, 238 00:11:17,909 --> 00:11:20,979 you're just filling them up with two electrons. 239 00:11:20,979 --> 00:11:24,816 Sigma star 2s with two electrons. 240 00:11:24,816 --> 00:11:28,620 Sigma 2p with two electrons. 241 00:11:28,620 --> 00:11:35,661 Pi, 2p with four electrons, and then pi 2p 242 00:11:35,661 --> 00:11:38,930 star with two electrons. 243 00:11:38,930 --> 00:11:41,667 That's how that looks. 244 00:11:41,667 --> 00:11:44,269 It's a little bit messy, but I hope you can read it. 245 00:11:44,269 --> 00:11:46,371 That's just reading up, right. 246 00:11:46,371 --> 00:11:49,441 It's the electron configuration of the MOs, 247 00:11:49,441 --> 00:11:51,677 just like we would write the s, p, d electron 248 00:11:51,677 --> 00:11:55,580 configuration of that, but this is a molecule. 249 00:11:55,580 --> 00:11:57,716 Now, sometimes you might, you know-- 250 00:11:57,716 --> 00:11:59,551 say there's a convention we use, which 251 00:11:59,551 --> 00:12:03,288 is that the pz is the sigma. 252 00:12:03,288 --> 00:12:05,390 Nobody can agree on it, so different textbooks say 253 00:12:05,390 --> 00:12:08,860 px but we're saying p-- if pz is sigma, 254 00:12:08,860 --> 00:12:14,399 then this would be like a sigma 2pz, right, and you might, 255 00:12:14,399 --> 00:12:16,101 if you really want to write this, 256 00:12:16,101 --> 00:12:19,471 you know, you might write that that's pi 2px if you really 257 00:12:19,471 --> 00:12:20,872 want to keep track of it. 258 00:12:20,872 --> 00:12:22,708 There's 2 orbitals in there. 259 00:12:22,708 --> 00:12:25,510 You didn't fill 1 orbital with 4 electrons, right? 260 00:12:25,510 --> 00:12:31,616 So this would be pi 2px and pi 2py 4, right? 261 00:12:31,616 --> 00:12:33,351 That's what's happening in there. 262 00:12:33,351 --> 00:12:34,319 OK. 263 00:12:34,319 --> 00:12:36,321 But the other thing you can see from the bot-- 264 00:12:36,321 --> 00:12:39,357 from this filling is, also, the bond order. 265 00:12:39,357 --> 00:12:41,493 And so for the bond order-- 266 00:12:41,493 --> 00:12:48,266 bond order, here you would have 1/2 times, 267 00:12:48,266 --> 00:12:49,701 and it's all of the-- 268 00:12:49,701 --> 00:12:52,604 remember, the bonder is all of the bonding electrons 269 00:12:52,604 --> 00:12:55,607 minus antibonding electrons divided by 2, right. 270 00:12:55,607 --> 00:12:58,143 And if it's zero, it's not a stable molecule. 271 00:12:58,143 --> 00:12:59,778 If it's greater than zero, it's stable. 272 00:12:59,778 --> 00:13:02,914 And the higher the bond order, the higher the bond strength. 273 00:13:02,914 --> 00:13:04,916 So that's also from Friday. 274 00:13:04,916 --> 00:13:13,024 And so this is 2 minus 2 plus 4 minus 2, and so you get 2. 275 00:13:13,024 --> 00:13:13,525 Nope. 276 00:13:13,525 --> 00:13:15,727 I missed a 2. 277 00:13:15,727 --> 00:13:20,665 Plus 2, plus 4 minus 2. 278 00:13:20,665 --> 00:13:23,668 2 minus 2, that kind of cancels out, right, 279 00:13:23,668 --> 00:13:28,907 plus 2, plus 4, minus 2, all divided by 2. 280 00:13:28,907 --> 00:13:33,378 So the bonder for oxy-- now, the bonder for No-- 281 00:13:33,378 --> 00:13:42,320 bond order for No is going to be 2.5. 282 00:13:42,320 --> 00:13:44,689 Well, that's kind of interesting, now, you can see-- 283 00:13:44,689 --> 00:13:45,190 OK. 284 00:13:45,190 --> 00:13:47,592 So No is stronger-- 285 00:13:47,592 --> 00:13:50,695 more strongly bound than O2, less strongly bound than N2. 286 00:13:50,695 --> 00:13:51,963 And it's kind of interesting. 287 00:13:51,963 --> 00:13:54,399 How can I make No a stronger-- 288 00:13:54,399 --> 00:13:56,334 a more strongly bound molecule? 289 00:13:56,334 --> 00:13:59,237 Well, I can take an electron away. 290 00:13:59,237 --> 00:14:01,506 It's a little bit counterintuitive, right? 291 00:14:01,506 --> 00:14:07,312 Because for No plus, the bond order 292 00:14:07,312 --> 00:14:10,515 goes up because the electron that I'd taken away 293 00:14:10,515 --> 00:14:12,717 was in an antibonding orbital. 294 00:14:12,717 --> 00:14:13,585 Right. 295 00:14:13,585 --> 00:14:16,888 So No plus actually has a stronger bond than No, 296 00:14:16,888 --> 00:14:18,423 even though it has one less electron. 297 00:14:18,423 --> 00:14:21,526 You get this all from just looking at which electrons 298 00:14:21,526 --> 00:14:24,863 are occupying which orbitals. 299 00:14:24,863 --> 00:14:29,734 In this case, you had in this very much not drawn to scale-- 300 00:14:29,734 --> 00:14:33,805 oh, boy-- figure, right. 301 00:14:33,805 --> 00:14:37,642 What you had was one up there. 302 00:14:37,642 --> 00:14:40,745 So if I take that out, my bond order increases. 303 00:14:40,745 --> 00:14:41,613 Right. 304 00:14:41,613 --> 00:14:42,747 OK. 305 00:14:42,747 --> 00:14:44,983 All right. 306 00:14:44,983 --> 00:14:47,552 And the last point I wanted to make about MO theory 307 00:14:47,552 --> 00:14:49,354 before we talk about hybridization 308 00:14:49,354 --> 00:14:52,190 is with one other example, and that's HTL. 309 00:14:55,293 --> 00:14:56,494 OK. 310 00:14:56,494 --> 00:14:58,296 So for HTL, you got something else 311 00:14:58,296 --> 00:14:59,865 happening that's important. 312 00:14:59,865 --> 00:15:03,401 So we just talked about electronegativity 313 00:15:03,401 --> 00:15:06,872 driving where the-- you know, that this is tilted. 314 00:15:06,872 --> 00:15:07,372 OK. 315 00:15:07,372 --> 00:15:08,273 Fine. 316 00:15:08,273 --> 00:15:10,842 And now we got the fact that chlorine 317 00:15:10,842 --> 00:15:12,644 comes into this situation. 318 00:15:12,644 --> 00:15:17,749 You know, it's like chlorine is like, hey, I got 7 electrons. 319 00:15:17,749 --> 00:15:22,520 And hydrogen is like, hey, I got 1. 320 00:15:22,520 --> 00:15:24,522 So how's this work, right. 321 00:15:24,522 --> 00:15:27,525 So this gets to what was brought up Friday, which 322 00:15:27,525 --> 00:15:31,062 is, there's another type of MO. 323 00:15:31,062 --> 00:15:33,531 And it's not bonding, and it's not antibonding, 324 00:15:33,531 --> 00:15:35,433 it's non-bonding. 325 00:15:35,433 --> 00:15:37,235 That is not the same as antibonding. 326 00:15:37,235 --> 00:15:40,772 Non-bonding doesn't take sides, it just is. 327 00:15:40,772 --> 00:15:44,309 Because the way this works is hydrogen comes at this-- 328 00:15:44,309 --> 00:15:44,809 OK. 329 00:15:44,809 --> 00:15:48,713 So hydrogen's up here with this 1s. 330 00:15:48,713 --> 00:15:51,549 Chlorine is, you know, let's say over here. 331 00:15:51,549 --> 00:15:55,820 It's got 3s filled, and it's got-- 332 00:15:55,820 --> 00:15:58,623 let's draw these here. 333 00:15:58,623 --> 00:15:59,357 OK. 334 00:15:59,357 --> 00:16:01,092 3p. 335 00:16:01,092 --> 00:16:06,464 And chlorine's got 7 electrons in the 3p. 336 00:16:06,464 --> 00:16:10,168 Do they-- do they all come together and form MOs? 337 00:16:10,168 --> 00:16:14,372 No, they can't, because there's only 1 on this side, right. 338 00:16:14,372 --> 00:16:18,910 So this 1 orbital will form-- 339 00:16:18,910 --> 00:16:23,281 let me make myself enough space so I'm 340 00:16:23,281 --> 00:16:25,116 going to exaggerate this a little bit. 341 00:16:25,116 --> 00:16:32,724 So this 1 orbital will form a sigma bond. 342 00:16:32,724 --> 00:16:37,495 Sigma 3p, sigma 3p bond. 343 00:16:37,495 --> 00:16:39,965 This would be a sigma 3p star. 344 00:16:39,965 --> 00:16:45,203 Now, that's exactly what we've already done, right, the sigma. 345 00:16:45,203 --> 00:16:51,576 But-- but-- oh, there's something a little interesting 346 00:16:51,576 --> 00:16:54,980 about this one, right, because it's an s. 347 00:16:54,980 --> 00:16:56,114 It's an s. 348 00:16:56,114 --> 00:17:00,685 But that's OK because the s can talk to a sigma p. 349 00:17:00,685 --> 00:17:02,020 This is -- we talked about this. 350 00:17:02,020 --> 00:17:04,255 The s can talk to this. 351 00:17:04,255 --> 00:17:05,790 That's OK. 352 00:17:05,790 --> 00:17:08,859 Because it's aligned, right. 353 00:17:08,859 --> 00:17:11,429 Now, but these guys don't have anyone to talk to. 354 00:17:11,429 --> 00:17:11,896 They don't. 355 00:17:11,896 --> 00:17:15,032 So they can't make their pi orbitals. 356 00:17:15,032 --> 00:17:16,434 They can't do that. 357 00:17:16,434 --> 00:17:18,336 And so they just stay there. 358 00:17:18,336 --> 00:17:22,173 These stay there exactly at the same place. 359 00:17:22,173 --> 00:17:23,875 They're not doing anything different. 360 00:17:23,875 --> 00:17:25,076 They're just hanging out. 361 00:17:25,076 --> 00:17:26,611 Those electrons are non-bonding. 362 00:17:26,611 --> 00:17:29,781 So these are not pi orbitals. 363 00:17:29,781 --> 00:17:33,051 Sigma and pi are special names. 364 00:17:33,051 --> 00:17:37,522 They refer to these orbitals of the molecule that 365 00:17:37,522 --> 00:17:40,658 involve the LCAO, the linear combination 366 00:17:40,658 --> 00:17:42,927 of the atomic orbitals. 367 00:17:42,927 --> 00:17:44,929 These do not. 368 00:17:44,929 --> 00:17:47,365 Nb. 369 00:17:47,365 --> 00:17:50,068 Nb. 370 00:17:50,068 --> 00:17:51,836 That's what we'll call them. 371 00:17:51,836 --> 00:17:53,671 Just to be very clear. 372 00:17:53,671 --> 00:17:55,040 Just to be very clear. 373 00:17:55,040 --> 00:17:56,574 Now, they're filled. 374 00:17:56,574 --> 00:18:00,378 They're filled, and they do not count in the bond order. 375 00:18:00,378 --> 00:18:06,684 By the way, this is, also, a non-bonding orbital. 376 00:18:06,684 --> 00:18:10,688 That's a non-bonding orbital. 377 00:18:10,688 --> 00:18:12,390 Non-bonding orbitals. 378 00:18:12,390 --> 00:18:13,925 These are not going to count. 379 00:18:13,925 --> 00:18:18,963 So in the bond order, you only have-- 380 00:18:18,963 --> 00:18:24,502 you have 1/2 times 2 minus 0 equals one. 381 00:18:24,502 --> 00:18:27,138 These do not participate in bonding. 382 00:18:27,138 --> 00:18:28,673 I got to fill this. 383 00:18:28,673 --> 00:18:31,509 2 electrons are in that one. 384 00:18:31,509 --> 00:18:31,976 OK. 385 00:18:31,976 --> 00:18:34,512 So that's another example of something 386 00:18:34,512 --> 00:18:37,482 that happens in these MO diagrams. 387 00:18:37,482 --> 00:18:40,418 One of them brought too many electrons to the party. 388 00:18:40,418 --> 00:18:43,321 And so there's no one to talk to. 389 00:18:43,321 --> 00:18:43,888 But it's OK. 390 00:18:43,888 --> 00:18:45,690 They're just going to stay there and wait. 391 00:18:45,690 --> 00:18:47,692 Maybe something else will come along. 392 00:18:47,692 --> 00:18:48,426 Right. 393 00:18:48,426 --> 00:18:49,527 OK. 394 00:18:49,527 --> 00:18:53,231 Now, that is, right there, what I just drew, look at that. 395 00:18:53,231 --> 00:18:56,701 2p 2s, and you get this thing, right. 396 00:18:56,701 --> 00:18:59,270 Oh, it's a beautiful molecular orbital between-- 397 00:18:59,270 --> 00:18:59,804 OK. 398 00:18:59,804 --> 00:19:00,271 Fine. 399 00:19:00,271 --> 00:19:03,875 It was a 1s and a 3p, but you get the point. 400 00:19:03,875 --> 00:19:07,378 It was a p oriented along the axis with sigma symmetry. 401 00:19:07,378 --> 00:19:09,647 That means if I look along the axis-- sorry, 402 00:19:09,647 --> 00:19:12,450 cylindrical symmetry, sigma means 403 00:19:12,450 --> 00:19:14,119 if I look around the axis, everything is 404 00:19:14,119 --> 00:19:16,654 the same, in a circle, right? 405 00:19:16,654 --> 00:19:17,288 Right. 406 00:19:17,288 --> 00:19:21,192 So-- but-- and so that's a nice sigma orbital 407 00:19:21,192 --> 00:19:23,128 between two different atoms. 408 00:19:23,128 --> 00:19:23,828 MO theory. 409 00:19:23,828 --> 00:19:26,397 But see the other thing that can happen that is something 410 00:19:26,397 --> 00:19:29,100 that I want you to know today, is 411 00:19:29,100 --> 00:19:34,205 that orbitals on the exact same atom can also do this. 412 00:19:34,205 --> 00:19:36,474 They can also do this. 413 00:19:36,474 --> 00:19:42,113 They can combine to form a new orbital. 414 00:19:42,113 --> 00:19:46,050 sp, same atom forms an sp orbital. 415 00:19:46,050 --> 00:19:47,952 It's called a hybrid orbital. 416 00:19:47,952 --> 00:19:49,787 So we're going to give a couple of examples. 417 00:19:49,787 --> 00:19:52,490 This is hybridization. 418 00:19:52,490 --> 00:19:53,558 Hybridization. 419 00:19:57,162 --> 00:19:59,297 And I can give a couple of examples, 420 00:19:59,297 --> 00:20:01,199 then my [INAUDIBLE] matters. 421 00:20:01,199 --> 00:20:12,710 So this is when two or more ao's that are similar in energy. 422 00:20:12,710 --> 00:20:15,213 They're similar, they're not the same but they're close. 423 00:20:15,213 --> 00:20:17,415 You know, you can't hybridize if one level's 424 00:20:17,415 --> 00:20:19,684 way up here and the other level's way down there. 425 00:20:19,684 --> 00:20:26,191 But if they're close, 2s 2p, then those orbitals 426 00:20:26,191 --> 00:20:26,724 can combine. 427 00:20:29,260 --> 00:20:31,996 And what they do is they combine to form, 428 00:20:31,996 --> 00:20:47,078 and this is critical, sets of equivalent orbitals properly 429 00:20:47,078 --> 00:20:48,246 oriented. 430 00:20:48,246 --> 00:20:49,280 This is really important. 431 00:20:49,280 --> 00:20:50,648 That's why I'm writing it all out. 432 00:20:50,648 --> 00:20:52,917 Properly, not property. 433 00:20:52,917 --> 00:20:58,089 Properly oriented to form bonds. 434 00:20:58,089 --> 00:21:04,128 Oh, this is such a big deal, to form bonds. 435 00:21:04,128 --> 00:21:07,665 It's the last word there, but I did it all caps to emphasize. 436 00:21:07,665 --> 00:21:09,867 Because that's what this is all about. 437 00:21:09,867 --> 00:21:13,271 You see, it-- now, let's take an example. 438 00:21:13,271 --> 00:21:14,939 I'm going to take an example of methane. 439 00:21:19,644 --> 00:21:20,945 Who brings what to the party? 440 00:21:20,945 --> 00:21:21,579 OK. 441 00:21:21,579 --> 00:21:22,747 I got H-- 442 00:21:22,747 --> 00:21:24,315 I've got 4 H's. 443 00:21:24,315 --> 00:21:31,889 H1s, H1s, H1s, OK. 444 00:21:31,889 --> 00:21:36,427 This is definitely getting repetitive. 445 00:21:36,427 --> 00:21:36,894 H1s. 446 00:21:39,697 --> 00:21:40,765 But I did it. 447 00:21:40,765 --> 00:21:41,666 There they are. 448 00:21:41,666 --> 00:21:44,335 And they come, and they're like, hey, carbon, what you got? 449 00:21:44,335 --> 00:21:46,604 And the carbon is like, OK, hold up. 450 00:21:46,604 --> 00:21:51,142 I got my 2s, that's here, and I got my-- 451 00:21:51,142 --> 00:21:56,981 all my 2p's, and what are we to do? 452 00:21:56,981 --> 00:21:58,716 What are we to do? 453 00:21:58,716 --> 00:22:01,619 How can these four hydrogens come 454 00:22:01,619 --> 00:22:05,423 and bond with the carbon given that it looks, 455 00:22:05,423 --> 00:22:10,528 at least, like the carbon isn't bringing the kind-- you know, 456 00:22:10,528 --> 00:22:11,629 how's it going to do this? 457 00:22:11,629 --> 00:22:13,097 And, also-- and this is critical. 458 00:22:13,097 --> 00:22:14,932 This is why I wrote it here. 459 00:22:14,932 --> 00:22:17,468 Properly oriented to form bonds. 460 00:22:17,468 --> 00:22:20,371 You see, because this taps into what we 461 00:22:20,371 --> 00:22:24,309 learned with VSEPR It does, because VSEPR 462 00:22:24,309 --> 00:22:27,211 says you got to not repel. 463 00:22:27,211 --> 00:22:30,214 Or, no, you're repelling, but try to minimize it. 464 00:22:30,214 --> 00:22:33,117 I mean, that's what's at the core of VSEPR. 465 00:22:33,117 --> 00:22:37,121 So what this system sees is a way out. 466 00:22:37,121 --> 00:22:39,657 And by way out, I mean a way to happiness. 467 00:22:39,657 --> 00:22:41,492 And by a way to happiness, I mean a way 468 00:22:41,492 --> 00:22:45,363 to lower energy where all 4 of these can bond to the carbon 469 00:22:45,363 --> 00:22:49,467 atom if it has 4 same bonds. 470 00:22:49,467 --> 00:22:54,872 If it had 4 same bonds, then it can orient them tetrahedrally 471 00:22:54,872 --> 00:23:00,311 and make VSEPR happy, minimize repulsions, right. 472 00:23:00,311 --> 00:23:02,513 And you get your methane molecule. 473 00:23:02,513 --> 00:23:07,251 So what ends up happening is this carbon atoms says, 474 00:23:07,251 --> 00:23:08,519 hold up. 475 00:23:08,519 --> 00:23:10,688 You 4 hydrogens, you wait there, I'm 476 00:23:10,688 --> 00:23:15,593 just going to go into the back and do a little reorganization, 477 00:23:15,593 --> 00:23:17,895 and I'm going to come in it with-- 478 00:23:17,895 --> 00:23:19,530 I'm going to say, well, if I had-- 479 00:23:19,530 --> 00:23:23,067 if my carbon atom comes at-- 480 00:23:23,067 --> 00:23:33,511 comes at it with 4 equal orbitals that look like this, 481 00:23:33,511 --> 00:23:39,016 those are called sp3, because I took all 3 p orbitals 482 00:23:39,016 --> 00:23:41,085 and I mix them up with my s orbital 483 00:23:41,085 --> 00:23:46,190 and I formed equivalent orbitals. 484 00:23:46,190 --> 00:23:50,027 Now, carbon comes out of the back room, and it's like, 485 00:23:50,027 --> 00:23:54,465 hydrogens, I'm ready, I can make a minimum energy, 486 00:23:54,465 --> 00:23:55,900 and I can follow VSEPR and we can 487 00:23:55,900 --> 00:23:59,203 have-- all have very, very low energy, compared 488 00:23:59,203 --> 00:24:01,839 to whatever else I could've done, if I stuck like that. 489 00:24:04,642 --> 00:24:06,644 What I'm really talking about when I'm talk-- 490 00:24:06,644 --> 00:24:07,211 OK. 491 00:24:07,211 --> 00:24:09,046 You might know carbon, you know, it 492 00:24:09,046 --> 00:24:10,948 doesn't go into the back room. 493 00:24:10,948 --> 00:24:11,449 It doesn't. 494 00:24:11,449 --> 00:24:12,917 But what is it doing? 495 00:24:12,917 --> 00:24:15,486 It's nothing more than solving its Schrodinger equation. 496 00:24:15,486 --> 00:24:17,488 That's what this is all about. 497 00:24:17,488 --> 00:24:20,591 You just change the boundary conditions. 498 00:24:20,591 --> 00:24:23,694 And so what happened-- that's all hybridization is. 499 00:24:23,694 --> 00:24:26,697 You're solving the Schrodinger equation all the time. 500 00:24:26,697 --> 00:24:29,600 We are always solving the Schrodinger equation 501 00:24:29,600 --> 00:24:30,968 all the time. 502 00:24:30,968 --> 00:24:32,503 And in this case, carbon said, well, 503 00:24:32,503 --> 00:24:36,140 how can I solve it and minimize my energy with the 4 hydrogens? 504 00:24:36,140 --> 00:24:38,342 This gives you the lowest energy. 505 00:24:38,342 --> 00:24:42,513 Because, now-- oh, I got a movie. 506 00:24:42,513 --> 00:24:45,216 Now, I can make those, see. 507 00:24:45,216 --> 00:24:46,150 So I have them-- 508 00:24:46,150 --> 00:24:47,251 I have a picture here. 509 00:24:47,251 --> 00:24:49,353 s and those three. 510 00:24:49,353 --> 00:24:51,689 And it says, how can I do it and minimize repulsions? 511 00:24:51,689 --> 00:24:52,723 This is how. 512 00:24:52,723 --> 00:24:55,526 Three equivalent-- 4 equivalent orbitals to make it sp3. 513 00:24:55,526 --> 00:24:57,161 And this is where I think a movie helps. 514 00:24:57,161 --> 00:24:57,895 So I'm going to play this. 515 00:24:57,895 --> 00:24:58,896 It's like a minute long. 516 00:24:58,896 --> 00:25:01,732 [VIDEO PLAYBACK] 517 00:25:01,732 --> 00:25:04,702 Each 2s orbital is a two lobe shape 518 00:25:04,702 --> 00:25:06,471 converging at the nucleus. 519 00:25:06,471 --> 00:25:07,371 - There's the 2s. 520 00:25:07,371 --> 00:25:10,475 So there are the three 2p orbitals. 521 00:25:10,475 --> 00:25:12,977 However, when hybridization occurs, 522 00:25:12,977 --> 00:25:16,080 the s and p orbitals cease to exist, 523 00:25:16,113 --> 00:25:19,884 They don't cease to exist, they just didn't-- 524 00:25:19,884 --> 00:25:21,285 it's a new boundary condition. 525 00:25:21,285 --> 00:25:22,520 You're solving the equation. 526 00:25:22,520 --> 00:25:23,020 Right. 527 00:25:23,020 --> 00:25:24,755 So just to keep that straight, right? 528 00:25:24,755 --> 00:25:25,490 These are the orbitals-- 529 00:25:25,556 --> 00:25:29,193 and the two sp3 orbitals have an entirely different shape. 530 00:25:29,193 --> 00:25:30,661 - That's true. 531 00:25:30,661 --> 00:25:33,030 We can see that orbital hybridization explains 532 00:25:33,030 --> 00:25:37,134 the VSEPR placement of carbons for VLANs electrons. 533 00:25:37,134 --> 00:25:40,638 Since all four 2sp3 orbitals are equivalent, 534 00:25:40,638 --> 00:25:44,675 each 2sp3 orbital repels the others with equal force, 535 00:25:44,675 --> 00:25:47,144 resulting in identical bond angles. 536 00:25:49,780 --> 00:25:52,116 The carbon atom only hybridizes when 537 00:25:52,116 --> 00:25:54,151 it is in a bonding situation. 538 00:25:54,151 --> 00:25:56,854 Here, four hydrogen atoms bond to carbon 539 00:25:56,854 --> 00:26:01,759 by overlapping their orbitals with carbon's hybrid orbitals. 540 00:26:01,759 --> 00:26:04,161 So what would be the reason for this? 541 00:26:04,161 --> 00:26:07,698 If we go back and see that both carbon and hydrogen have 542 00:26:07,698 --> 00:26:10,868 unpaired electrons, the overlap allows 543 00:26:10,868 --> 00:26:14,071 the electrons to pair, and thus go to a lower potential energy. 544 00:26:14,071 --> 00:26:14,705 [END PLAYBACK] 545 00:26:14,705 --> 00:26:16,774 Oh, that's such a beautiful place to stop. 546 00:26:16,774 --> 00:26:18,409 Lower potential energy. 547 00:26:18,409 --> 00:26:20,344 Happier. 548 00:26:20,344 --> 00:26:22,446 That's what this is all about. 549 00:26:22,446 --> 00:26:22,947 OK. 550 00:26:22,947 --> 00:26:25,816 So I-- you know, like I said, you can see now the difference, 551 00:26:25,816 --> 00:26:27,952 right, if you just watch-- it's one minute long, 552 00:26:27,952 --> 00:26:29,620 and I think it really brings it to life. 553 00:26:29,620 --> 00:26:32,056 So if you're, again, want to see this a little bit 554 00:26:32,056 --> 00:26:33,724 more conceptually, these movies are good. 555 00:26:33,724 --> 00:26:37,695 I have one more movie I'll show you that's like a minute long. 556 00:26:37,695 --> 00:26:38,195 OK. 557 00:26:38,195 --> 00:26:39,897 Now, the thing is-- so what we just 558 00:26:39,897 --> 00:26:42,833 did is we did carbon hybridizes to sp3. 559 00:26:42,833 --> 00:26:45,202 It's called sp3 because you're bringing 3p orbitals 560 00:26:45,202 --> 00:26:47,838 and mixing them with s to form 4. 561 00:26:47,838 --> 00:26:50,274 And that allowed it to do this. 562 00:26:50,274 --> 00:26:54,011 But, you see, if I had ethane, which is C2H6, 563 00:26:54,011 --> 00:26:55,446 it's the same thing. 564 00:26:55,446 --> 00:26:58,215 Now-- because, basically, what's happening? 565 00:26:58,215 --> 00:27:02,086 A carbon atom comes into this system of ethane, and it says, 566 00:27:02,086 --> 00:27:06,390 I need 4 bonds that are kind of equivalent-ish. 567 00:27:06,390 --> 00:27:06,991 All right. 568 00:27:06,991 --> 00:27:08,659 I got to give one to each hydrogen 569 00:27:08,659 --> 00:27:12,229 and I've got to give one to that other carbon over there. 570 00:27:12,229 --> 00:27:15,499 And by doing that, it can minimize its energy, 571 00:27:15,499 --> 00:27:18,302 it can minimize repulsions, it can be the happiest molecule 572 00:27:18,302 --> 00:27:19,303 it can be. 573 00:27:19,303 --> 00:27:24,308 But to do that, carbon must have these four equivalent 574 00:27:24,308 --> 00:27:25,743 sigma like bonds. 575 00:27:25,743 --> 00:27:28,112 It must be able to form those four equivalency. 576 00:27:28,112 --> 00:27:31,248 So that's very similar to methane, except that in this-- 577 00:27:31,248 --> 00:27:35,052 so, also, ethane will be sp3 hybridized. 578 00:27:35,052 --> 00:27:38,656 It will have sp3 hybridized orbitals. 579 00:27:38,656 --> 00:27:40,791 But then, and you know it's coming, right, 580 00:27:40,791 --> 00:27:44,161 so ethane has C2H6. 581 00:27:44,161 --> 00:27:48,165 But what if now I've got ethylene. 582 00:27:48,165 --> 00:27:50,134 I think I have-- maybe I have a picture of it. 583 00:27:50,134 --> 00:27:50,901 Do I have a picture of it? 584 00:27:50,901 --> 00:27:51,435 Yeah. 585 00:27:51,435 --> 00:27:52,536 Oh, there it is. 586 00:27:52,536 --> 00:27:53,337 Ethylene. 587 00:27:53,337 --> 00:27:54,405 Ethylene is used. 588 00:27:54,405 --> 00:27:58,542 This tiny molecule is 2 carbons and 4 hydrogen instead of 6. 589 00:27:58,542 --> 00:28:00,778 This is used in so many applications I can't possibly 590 00:28:00,778 --> 00:28:01,278 list them. 591 00:28:01,278 --> 00:28:04,715 If polyethylene is a polymer made out of this as a base, 592 00:28:04,715 --> 00:28:07,718 we will polymerize this a little bit later in the semester 593 00:28:07,718 --> 00:28:09,420 when we talk about polymers. 594 00:28:09,420 --> 00:28:11,922 It's also used in the back of your supermarket in case 595 00:28:11,922 --> 00:28:12,823 you didn't know that. 596 00:28:12,823 --> 00:28:15,559 Very soon-- actually, kind of almost now-ish, 597 00:28:15,559 --> 00:28:18,663 most of the fruit we get will be super green when it gets here. 598 00:28:18,663 --> 00:28:24,301 And then they use ethylene to actually induce, sadly, 599 00:28:24,301 --> 00:28:25,469 the brightness. 600 00:28:25,469 --> 00:28:27,571 Doesn't taste as good. 601 00:28:27,571 --> 00:28:28,472 But, anyway-- OK. 602 00:28:28,472 --> 00:28:32,476 Now, but for ethylene, you've got a different situation. 603 00:28:32,476 --> 00:28:36,914 Because for ethylene, each carbon atom needs 3 bonds. 604 00:28:36,914 --> 00:28:44,722 Each carbon atom needs 3 equivalent bonds. 605 00:28:48,859 --> 00:28:52,863 And it can do that, too. 606 00:28:52,863 --> 00:28:58,969 So, for C2H4, each carbon atom needs 3 equivalent bonds, 607 00:28:58,969 --> 00:29:01,405 and it can do that if it hybridizes 608 00:29:01,405 --> 00:29:03,040 in the sp2 hybridization. 609 00:29:03,040 --> 00:29:04,141 So let's draw that, right. 610 00:29:04,141 --> 00:29:08,746 So these are the original orbitals of carbon. 611 00:29:08,746 --> 00:29:14,318 And they will go to 3 sp2 orbitals. 612 00:29:16,854 --> 00:29:20,791 Notice, I can put one electron in each ready for action. 613 00:29:20,791 --> 00:29:22,259 Ready for bonding. 614 00:29:22,259 --> 00:29:25,696 One electron in each of these equivalent hybrid orbitals, 615 00:29:25,696 --> 00:29:26,530 sp2. 616 00:29:26,530 --> 00:29:28,165 And I got one left over. 617 00:29:28,165 --> 00:29:30,634 Ho, ho, oh. 618 00:29:30,634 --> 00:29:33,070 One left over. 619 00:29:33,070 --> 00:29:36,073 But the one left over is a p orbital 620 00:29:36,073 --> 00:29:37,908 that didn't get in on the hybridization. 621 00:29:37,908 --> 00:29:40,010 But that's OK. 622 00:29:40,010 --> 00:29:40,811 That's OK. 623 00:29:40,811 --> 00:29:42,446 These are p, right. 624 00:29:42,446 --> 00:29:46,183 So this is s and this is p2s 2p. 625 00:29:46,183 --> 00:29:47,651 And that's a p orbital right there. 626 00:29:47,651 --> 00:29:49,553 Those are my hybrids, and that's a 2p orbital. 627 00:29:52,256 --> 00:29:54,892 There's another 2p orbital on the other carbon. 628 00:29:54,892 --> 00:29:56,260 Also, got left out. 629 00:29:56,260 --> 00:29:58,095 Now, I only needed 3 because, you 630 00:29:58,095 --> 00:30:02,466 see, I formed this nice spatially maximize 631 00:30:02,466 --> 00:30:04,835 to minimize repulsion, right, separation, 632 00:30:04,835 --> 00:30:07,304 maximize to minimize repulsion so it's a planar-- 633 00:30:07,304 --> 00:30:10,040 oh, but it's a planar for another reason. 634 00:30:10,040 --> 00:30:13,110 Because each of these carbon atoms has a p orbital, 635 00:30:13,110 --> 00:30:18,682 and we know that 2p orbitals can form a pi bond, right? 636 00:30:18,682 --> 00:30:20,117 And I have a picture of that. 637 00:30:20,117 --> 00:30:22,219 That's exactly what they do. 638 00:30:22,219 --> 00:30:26,023 So this is the sigma. 639 00:30:26,023 --> 00:30:28,592 The hybrid orbitals are sigma, right, 640 00:30:28,592 --> 00:30:31,495 because they're along the axis, and look at them. 641 00:30:31,495 --> 00:30:35,800 If I look down this axis, I can draw a circle, 642 00:30:35,800 --> 00:30:38,936 and there's full cylindrical symmetry, right. 643 00:30:38,936 --> 00:30:41,705 But I've got this left over p orbital 644 00:30:41,705 --> 00:30:44,208 here on each carbon atom. 645 00:30:44,208 --> 00:30:46,310 That's that one there. 646 00:30:46,310 --> 00:30:49,580 And I didn't need it to do this but it's still there. 647 00:30:49,580 --> 00:30:51,148 And so it forms a bond. 648 00:30:51,148 --> 00:30:53,150 It forms a bond. 649 00:30:53,150 --> 00:30:53,684 Right. 650 00:30:53,684 --> 00:30:55,986 It forms a pi bond. 651 00:30:55,986 --> 00:30:59,623 So that p with the p from the other one forms 652 00:30:59,623 --> 00:31:02,893 a pi and a pi star, right, in the MOs, 653 00:31:02,893 --> 00:31:05,696 and you occupy the pi with the two electrons. 654 00:31:05,696 --> 00:31:08,432 And that's a bond. 655 00:31:08,432 --> 00:31:10,100 So in this you've got-- 656 00:31:10,100 --> 00:31:14,338 you've got a bond from this that's above or below-- 657 00:31:14,338 --> 00:31:18,008 in this orientation, it's above or below the plane. 658 00:31:18,008 --> 00:31:19,643 And you've got a bond from this. 659 00:31:19,643 --> 00:31:21,178 So you've got a double bond. 660 00:31:21,178 --> 00:31:24,281 That's exactly what we know already, 661 00:31:24,281 --> 00:31:26,984 but we know so much more now. 662 00:31:26,984 --> 00:31:28,018 We know so much more. 663 00:31:28,018 --> 00:31:32,022 Because-- because, now, we know that it's not just two-- 664 00:31:32,022 --> 00:31:33,858 you know, two bonds and four electrons, 665 00:31:33,858 --> 00:31:35,492 we know that they have shape to them. 666 00:31:35,492 --> 00:31:37,194 We know that they have structure to them, 667 00:31:37,194 --> 00:31:40,197 and we know that those bonds are different. 668 00:31:40,197 --> 00:31:43,667 These are pi bonds, and that's a sigma bond. 669 00:31:43,667 --> 00:31:44,568 Right. 670 00:31:44,568 --> 00:31:47,838 And you, also, know why this molecule stays planar. 671 00:31:47,838 --> 00:31:51,408 Because if I try to twist it, then those p orbitals 672 00:31:51,408 --> 00:31:53,143 won't align, right. 673 00:31:53,143 --> 00:31:54,211 It's like a little spring. 674 00:31:54,211 --> 00:31:56,580 If I-- if I try to twist it, it's going to go right back. 675 00:31:56,580 --> 00:31:59,283 Because it's minimum in energy is when these things 676 00:31:59,283 --> 00:32:01,051 can maximize their overlap. 677 00:32:01,051 --> 00:32:01,518 All right. 678 00:32:01,518 --> 00:32:03,787 So that's going to stay planar. 679 00:32:03,787 --> 00:32:06,023 OK. 680 00:32:06,023 --> 00:32:12,529 Now-- and so for this case, you've got a double bond. 681 00:32:12,529 --> 00:32:21,805 So this is double bond, and I think I have a little carbon, 682 00:32:21,805 --> 00:32:24,875 carbon, double bond. 683 00:32:24,875 --> 00:32:26,777 And I think I've got a video to show this, 684 00:32:26,777 --> 00:32:28,946 because this is another case where, you know, 685 00:32:28,946 --> 00:32:30,781 again, I just want to make sure you guys get 686 00:32:30,781 --> 00:32:32,449 the intuition here, and I thought this is 687 00:32:32,449 --> 00:32:34,451 a pretty cool animation of sp2. 688 00:32:34,451 --> 00:32:35,719 So I'll play it for a minute. 689 00:32:35,719 --> 00:32:36,420 [VIDEO PLAYBACK] 690 00:32:36,420 --> 00:32:37,521 [INAUDIBLE] bonds. 691 00:32:37,521 --> 00:32:41,992 The one 2s and two of the 2p orbitals hybridize. 692 00:32:41,992 --> 00:32:42,893 Consequently-- 693 00:32:42,893 --> 00:32:43,894 - That's cool animation. 694 00:32:43,894 --> 00:32:46,697 --this hybridization is termed as sp2 hybridization. 695 00:32:46,697 --> 00:32:48,365 - Look at that. 696 00:32:48,365 --> 00:32:52,569 The hybridization leads to the formation of 3 [INAUDIBLE] 697 00:32:52,569 --> 00:32:53,904 sp2 hybrid orbitals. 698 00:32:57,007 --> 00:33:01,712 As you can see, each sp2 hybrid orbital is bilobed. 699 00:33:01,712 --> 00:33:03,914 One lobe bigger than the other. 700 00:33:03,914 --> 00:33:06,550 The half-filled p orbital, which was not 701 00:33:06,550 --> 00:33:10,120 involved in hybridization, flies at right angles 702 00:33:10,120 --> 00:33:14,024 to the plane of the equilateral triangle. 703 00:33:14,024 --> 00:33:16,560 Now, let us understand how this hybridized 704 00:33:16,560 --> 00:33:21,031 state results in the formation of a double bond. 705 00:33:21,031 --> 00:33:26,136 For this, imagine a similar sp2 hybridized carbon atom 706 00:33:26,136 --> 00:33:28,038 approaching this carbon atom. 707 00:33:28,038 --> 00:33:31,608 As these atoms come closer, an orbital overlap 708 00:33:31,608 --> 00:33:35,512 takes place along the internuclear axes. 709 00:33:35,512 --> 00:33:38,615 This bond is called a sigma bond. 710 00:33:38,615 --> 00:33:41,518 At this stage, the unhybridized p orbitals 711 00:33:41,518 --> 00:33:45,689 which lie above and below the plane of the sigma bond, also 712 00:33:45,689 --> 00:33:49,059 come very close to each other and overlap laterally, 713 00:33:49,059 --> 00:33:52,863 resulting in the formation of a pi bond between the two carbon 714 00:33:52,863 --> 00:33:53,330 atoms. 715 00:33:53,330 --> 00:33:53,764 [END PLAYBACK] 716 00:33:53,764 --> 00:33:54,264 All right. 717 00:33:54,264 --> 00:33:54,765 OK. 718 00:33:54,765 --> 00:33:58,435 So I thought about it. 719 00:33:58,435 --> 00:34:01,638 I watched that movie, of course, many times over the weekend. 720 00:34:01,638 --> 00:34:04,408 And I thought about can I animate, you know, 721 00:34:04,408 --> 00:34:07,044 the electrons like that and do the-- and I-- 722 00:34:07,044 --> 00:34:08,012 I think I could. 723 00:34:08,012 --> 00:34:10,813 But I don't know that it would be a good use of our time. 724 00:34:10,813 --> 00:34:13,784 So I thought that they did a pretty good job of bringing it 725 00:34:13,784 --> 00:34:14,918 to life. 726 00:34:14,918 --> 00:34:18,722 Now, this is a great time for me to tell you 727 00:34:18,722 --> 00:34:20,824 about my why this matters. 728 00:34:20,824 --> 00:34:23,159 And, of course, the sp2 carbon atom 729 00:34:23,159 --> 00:34:29,733 matters because of drinking water, of course. 730 00:34:29,733 --> 00:34:31,368 And, you know, this is a well-- 731 00:34:31,368 --> 00:34:34,938 in a district in India where more than 50% of the wells 732 00:34:34,938 --> 00:34:37,306 exceed the WHO limits for arsenic 733 00:34:37,306 --> 00:34:41,277 by around a factor of 5. 734 00:34:41,277 --> 00:34:44,380 1.8 billion people in the world drink fecally contaminated 735 00:34:44,380 --> 00:34:46,016 water on a daily basis. 736 00:34:46,016 --> 00:34:49,953 600 million people boil their water in the world. 737 00:34:49,953 --> 00:34:51,755 Boiling doesn't help with arsenic, though, 738 00:34:51,755 --> 00:34:54,123 arsenic just stays in the boiled water. 739 00:34:54,123 --> 00:34:57,327 It kills bacteria, but it doesn't help with toxic-- 740 00:34:57,327 --> 00:34:59,830 toxic elements. 741 00:34:59,830 --> 00:35:01,965 If you look at the world as a whole, 742 00:35:01,965 --> 00:35:06,136 and you look at sort of where there are water-- 743 00:35:06,136 --> 00:35:10,040 water crisis, where the water crisis is at this level, 744 00:35:10,040 --> 00:35:14,578 it's a little over 3 and 1/2 billion people. 745 00:35:14,578 --> 00:35:19,716 And in those countries, almost 185 or so countries, 746 00:35:19,716 --> 00:35:21,985 where this is a serious problem, if you 747 00:35:21,985 --> 00:35:26,723 look at the cost of disease, and the cause of death 748 00:35:26,723 --> 00:35:30,994 in those countries, 70% to 80% of all disease and almost 30% 749 00:35:30,994 --> 00:35:34,131 of all death can be attributed to the water quality. 750 00:35:34,131 --> 00:35:34,798 Right. 751 00:35:34,798 --> 00:35:38,001 So when I talk about water as a problem, 752 00:35:38,001 --> 00:35:40,604 I really mean it's a serious problem. 753 00:35:40,604 --> 00:35:43,540 It's a problem of life or death. 754 00:35:43,540 --> 00:35:47,077 Now, this is-- to get fresh drinking water, 755 00:35:47,077 --> 00:35:49,646 if you look at the planet, and you say, well, where 756 00:35:49,646 --> 00:35:51,381 is the water on this planet? 757 00:35:51,381 --> 00:35:54,017 Where is the water on this planet? 758 00:35:54,017 --> 00:36:01,158 I like this picture because we consume water volumetrically, 759 00:36:01,158 --> 00:36:02,759 not in an area, right? 760 00:36:02,759 --> 00:36:05,362 We use water as a volume, and this 761 00:36:05,362 --> 00:36:10,200 is the water we have on this precious planet as a volume. 762 00:36:10,200 --> 00:36:14,004 This bubble here is all of the ocean water. 763 00:36:14,004 --> 00:36:17,141 It's about 70-- it's about 97% of all the water. 764 00:36:17,141 --> 00:36:21,578 That bubble there is freshwater that is inaccessible. 765 00:36:21,578 --> 00:36:22,412 It's frozen. 766 00:36:22,412 --> 00:36:24,214 And this one here, you can't really see it, 767 00:36:24,214 --> 00:36:25,949 there is another dot there. 768 00:36:25,949 --> 00:36:28,218 That's less than 1% of the world's water. 769 00:36:28,218 --> 00:36:30,654 That is our drinking water ecosystem 770 00:36:30,654 --> 00:36:33,957 that is what we are destroying. 771 00:36:33,957 --> 00:36:35,192 And-- so what-- 772 00:36:35,192 --> 00:36:35,692 OK. 773 00:36:35,692 --> 00:36:39,930 So there's a lot of things we can try to do about this. 774 00:36:39,930 --> 00:36:41,331 One of the things we can try to do 775 00:36:41,331 --> 00:36:43,867 is to see if we can tap into this 776 00:36:43,867 --> 00:36:47,070 in a way that's more affordable and more efficient. 777 00:36:47,070 --> 00:36:51,408 Because there's a lot of water here, right, and use that. 778 00:36:51,408 --> 00:36:54,444 But the problem is, if you look at the cost of desalination 779 00:36:54,444 --> 00:36:57,681 today as opposed to the cost-- that's desalination. 780 00:36:57,681 --> 00:36:59,082 If you look at the cost as opposed 781 00:36:59,082 --> 00:37:01,251 to just digging water out of a well, 782 00:37:01,251 --> 00:37:02,886 like the one I just showed you in India, 783 00:37:02,886 --> 00:37:04,955 it's over a factor of 10. 784 00:37:04,955 --> 00:37:05,722 Still. 785 00:37:05,722 --> 00:37:08,992 And, in fact, one of the big issues with desalination 786 00:37:08,992 --> 00:37:12,462 isn't just the total cost or the operating costs, 787 00:37:12,462 --> 00:37:13,530 but the capital cost. 788 00:37:13,530 --> 00:37:17,734 How do you build this plant in the first place? 789 00:37:17,734 --> 00:37:22,539 And so it takes too much money. 790 00:37:22,539 --> 00:37:26,210 If you look at the thing that's at the heart of desalination, 791 00:37:26,210 --> 00:37:28,011 it's a filter, right. 792 00:37:28,011 --> 00:37:28,612 It's a filter. 793 00:37:28,612 --> 00:37:30,013 And I talked about this in my last, 794 00:37:30,013 --> 00:37:32,849 why this matters, when I talk about separations, 795 00:37:32,849 --> 00:37:35,018 and I promised that in my next why does this matter, 796 00:37:35,018 --> 00:37:36,553 I'd talk about water. 797 00:37:36,553 --> 00:37:37,120 Right. 798 00:37:37,120 --> 00:37:38,755 Which is what I'm doing. 799 00:37:38,755 --> 00:37:40,190 If you look at a desal plant, this 800 00:37:40,190 --> 00:37:42,392 is one of the world's largest, this is a plant called 801 00:37:42,392 --> 00:37:44,494 the Hadera plant in Israel, and you 802 00:37:44,494 --> 00:37:46,396 look at what their costs are that-- remember, 803 00:37:46,396 --> 00:37:48,999 the costs digits-- half of that cost-- almost half of the cost 804 00:37:48,999 --> 00:37:50,667 isn't just energy. 805 00:37:50,667 --> 00:37:54,104 And almost all of that energy is in pushing salt water 806 00:37:54,104 --> 00:37:55,672 through a filter. 807 00:37:55,672 --> 00:37:57,774 Through a membrane. 808 00:37:57,774 --> 00:37:59,676 That's called a reverse osmosis membrane, 809 00:37:59,676 --> 00:38:03,647 because you're going against the osmotic pressure. 810 00:38:03,647 --> 00:38:06,216 And if you look at the membrane itself-- 811 00:38:06,216 --> 00:38:07,784 this is a picture of it, it's actually 812 00:38:07,784 --> 00:38:11,588 a very small layer on top of this active layer that 813 00:38:11,588 --> 00:38:13,023 does all the work-- 814 00:38:13,023 --> 00:38:15,325 it's not a very good design. 815 00:38:15,325 --> 00:38:19,963 In fact, membranes for desalination are pretty bad. 816 00:38:19,963 --> 00:38:21,164 Right. 817 00:38:21,164 --> 00:38:23,800 They kind of do everything worse than they should, 818 00:38:23,800 --> 00:38:27,170 except that they work, which is good, and they're cheap, 819 00:38:27,170 --> 00:38:28,405 $1.00 a square foot. 820 00:38:28,405 --> 00:38:30,607 But, see, they're very-- they take much more energy 821 00:38:30,607 --> 00:38:32,542 than you need. 822 00:38:32,542 --> 00:38:34,611 They foul up very easily. 823 00:38:34,611 --> 00:38:37,047 And then that means stuff gets kind of, you know, 824 00:38:37,047 --> 00:38:38,548 stuck in them. 825 00:38:38,548 --> 00:38:41,985 And then you can't take it-- you can't clean them 826 00:38:41,985 --> 00:38:44,621 because these polyamide membranes, which 827 00:38:44,621 --> 00:38:47,357 are the same polymer used in these membranes for 50 years, 828 00:38:47,357 --> 00:38:50,460 haven't changed, the material. 829 00:38:50,460 --> 00:38:52,929 Those polyamide membranes are destroyed by chlorine. 830 00:38:52,929 --> 00:38:56,166 So even in a desal plant-- in a desal plant, 831 00:38:56,166 --> 00:38:59,936 if you have drinking water in your feed stream, 832 00:38:59,936 --> 00:39:02,205 drinking water has six parts per million chlorine. 833 00:39:02,205 --> 00:39:03,373 That's not much. 834 00:39:03,373 --> 00:39:07,177 They still will go through the cost to remove it. 835 00:39:07,177 --> 00:39:08,578 They will remove it from the feed. 836 00:39:08,578 --> 00:39:09,079 Why? 837 00:39:09,079 --> 00:39:11,715 Because if you leave that little amount of chlorine in the feed, 838 00:39:11,715 --> 00:39:12,949 these membranes get destroyed. 839 00:39:12,949 --> 00:39:15,952 By the way, there's 40,000 of these membranes in this plant. 840 00:39:15,952 --> 00:39:19,723 Each one is 2 meters long and 40 square meters of area. 841 00:39:19,723 --> 00:39:24,194 So-- so these are so delicate that you can't really 842 00:39:24,194 --> 00:39:25,729 clean them well. 843 00:39:25,729 --> 00:39:28,598 And that's part of what the cost of a plant involves. 844 00:39:28,598 --> 00:39:30,667 That's part of what the cost of a plant involves. 845 00:39:30,667 --> 00:39:32,669 Now, this would be like a plant, right, you 846 00:39:32,669 --> 00:39:36,039 have sea water coming in and, you know-- and then 847 00:39:36,039 --> 00:39:37,874 you've got your membrane module that's taking 848 00:39:37,874 --> 00:39:39,676 the salt out of the water. 849 00:39:39,676 --> 00:39:40,844 And then the product water. 850 00:39:40,844 --> 00:39:44,514 But because this filter is so delicate-- 851 00:39:44,514 --> 00:39:45,682 there's the picture-- 852 00:39:45,682 --> 00:39:47,150 because that filter is so delicate, 853 00:39:47,150 --> 00:39:49,686 you actually have to add a whole lot more to the plant. 854 00:39:49,686 --> 00:39:52,956 So much of a desal plant is built around essentially 855 00:39:52,956 --> 00:39:55,625 protecting this membrane. 856 00:39:55,625 --> 00:39:56,693 So that's cost. 857 00:39:56,693 --> 00:39:58,395 That's cost. 858 00:39:58,395 --> 00:39:58,895 Right. 859 00:39:58,895 --> 00:40:01,498 A better membrane could change this. 860 00:40:01,498 --> 00:40:03,800 But like I said, the membrane-- oh, there it is. 861 00:40:03,800 --> 00:40:07,437 You can't Snapchat on that. 862 00:40:07,437 --> 00:40:08,071 Snapchat? 863 00:40:08,071 --> 00:40:09,639 What is it that people do today? 864 00:40:09,639 --> 00:40:10,440 Not Snapchat. 865 00:40:10,440 --> 00:40:11,174 Yeah, Snapchat. 866 00:40:11,174 --> 00:40:11,708 Yeah. 867 00:40:11,708 --> 00:40:12,175 OK. 868 00:40:12,175 --> 00:40:13,009 Thank you. 869 00:40:13,009 --> 00:40:14,277 You can't Snapchat on that. 870 00:40:14,277 --> 00:40:16,913 That's what I meant. 871 00:40:16,913 --> 00:40:19,082 I know it's not My Space, but I don't know-- 872 00:40:19,082 --> 00:40:25,188 but, anyway, this is like even-- you know, when I look at-- 873 00:40:25,188 --> 00:40:28,024 at membranes today as a material scientist and materials 874 00:40:28,024 --> 00:40:30,026 chemists, all of your membranes, I think, 875 00:40:30,026 --> 00:40:31,661 that's what it looks like. 876 00:40:31,661 --> 00:40:32,195 Why? 877 00:40:32,195 --> 00:40:33,397 Doesn't have to be the case. 878 00:40:33,397 --> 00:40:35,832 We can do so much better. 879 00:40:35,832 --> 00:40:36,933 And so-- OK. 880 00:40:36,933 --> 00:40:39,102 Energy costs goes into pretreatment, secondary 881 00:40:39,102 --> 00:40:41,571 treatment, and this is where this comes back. 882 00:40:41,571 --> 00:40:46,576 This beautiful material that we have now understood more 883 00:40:46,576 --> 00:40:47,544 than we did before. 884 00:40:47,544 --> 00:40:49,479 Because, remember, before I showed 885 00:40:49,479 --> 00:40:51,114 you graphene and I showed you-- 886 00:40:51,114 --> 00:40:52,115 no, I showed you benzene. 887 00:40:54,651 --> 00:40:57,220 And we talked about it as a Lewis resonant structure, 888 00:40:57,220 --> 00:40:57,921 remember? 889 00:40:57,921 --> 00:40:58,422 Right. 890 00:40:58,422 --> 00:41:01,658 A Lewis resonant structure to help explain how it looked. 891 00:41:01,658 --> 00:41:06,062 You know, gra-- graphene does not have alternating bonds. 892 00:41:06,062 --> 00:41:08,231 Remember, that's what we talked about before. 893 00:41:08,231 --> 00:41:11,034 It's a Lewis resonant structure. 894 00:41:11,034 --> 00:41:13,136 So it lowers its energy by having 895 00:41:13,136 --> 00:41:17,574 two sets of structures that have sort of alternating bonds. 896 00:41:17,574 --> 00:41:19,576 We talked about it in the context of benzene. 897 00:41:19,576 --> 00:41:22,612 But, see, now you know so much more. 898 00:41:22,612 --> 00:41:23,847 You know so much more. 899 00:41:23,847 --> 00:41:27,884 Because, now, you know why graphene is so special. 900 00:41:27,884 --> 00:41:29,886 You know why graphene is so special. 901 00:41:29,886 --> 00:41:33,156 It actually is the hybridization. 902 00:41:33,156 --> 00:41:34,157 It's the hybridization. 903 00:41:34,157 --> 00:41:36,893 Because on top, and on the bottom, 904 00:41:36,893 --> 00:41:41,331 of a single atom of a single sheet of graphene, 905 00:41:41,331 --> 00:41:44,367 you've got pi bonding all the way. 906 00:41:44,367 --> 00:41:47,370 Those pi bands are going across the whole surface. 907 00:41:47,370 --> 00:41:49,706 And those electrons are critical. 908 00:41:49,706 --> 00:41:51,641 Those electrons that occupy those [INAUDIBLE] 909 00:41:51,641 --> 00:41:57,647 are critical to the very special properties that graphene has. 910 00:41:57,647 --> 00:42:00,016 So you now know the secret. 911 00:42:00,016 --> 00:42:01,751 It's sp2 hybridization. 912 00:42:01,751 --> 00:42:04,287 And, you know, this has allowed us-- 913 00:42:04,287 --> 00:42:06,490 this has-- you might tell I'm kind of 914 00:42:06,490 --> 00:42:07,824 passionate about this problem. 915 00:42:07,824 --> 00:42:09,359 Partly impassioned passion about a lot of problems 916 00:42:09,359 --> 00:42:10,927 but, also, we happen to work on this, 917 00:42:10,927 --> 00:42:12,629 and we have been developing this. 918 00:42:12,629 --> 00:42:14,731 This is like the ultimate membrane. 919 00:42:14,731 --> 00:42:16,833 I can soak this in chlorine overnight. 920 00:42:16,833 --> 00:42:18,668 I can put it in negative pH solutions. 921 00:42:18,668 --> 00:42:20,103 I can heat it up. 922 00:42:20,103 --> 00:42:22,038 It doesn't degrade. 923 00:42:22,038 --> 00:42:26,042 And we have figured out how to poke holes in it 924 00:42:26,042 --> 00:42:28,211 at just the right size, or to stitch it 925 00:42:28,211 --> 00:42:33,216 together so that maybe you can filter particles by the flow 926 00:42:33,216 --> 00:42:34,951 in between these sheets. 927 00:42:34,951 --> 00:42:36,686 Right. 928 00:42:36,686 --> 00:42:38,288 And this material, as a membrane, 929 00:42:38,288 --> 00:42:41,525 is so promising that we've actually 930 00:42:41,525 --> 00:42:44,227 started to commercialize it as of the last year. 931 00:42:44,227 --> 00:42:46,596 And I think this is really going to make a big difference 932 00:42:46,596 --> 00:42:48,798 in a lot of areas. 933 00:42:48,798 --> 00:42:49,599 Why? 934 00:42:49,599 --> 00:42:52,135 Because of sp2 hybridization. 935 00:42:52,135 --> 00:42:53,236 That is why. 936 00:42:53,236 --> 00:42:55,772 That is why this is such a special material. 937 00:42:55,772 --> 00:42:56,339 OK. 938 00:42:56,339 --> 00:42:58,441 That's my why this matters. 939 00:42:58,441 --> 00:43:00,610 Now-- oh, we did see 2H6. 940 00:43:00,610 --> 00:43:01,144 There it is. 941 00:43:01,144 --> 00:43:02,345 We did see 2H4. 942 00:43:02,345 --> 00:43:03,046 There it is. 943 00:43:03,046 --> 00:43:06,149 Look at that extra pi bond, not animated this time. 944 00:43:06,149 --> 00:43:09,619 And, of course, you can go on and you could do see C2H2, 945 00:43:09,619 --> 00:43:12,055 and you can imagine what happens in this case, 946 00:43:12,055 --> 00:43:14,357 is what you would expect. 947 00:43:14,357 --> 00:43:15,525 Is what you would expect. 948 00:43:15,525 --> 00:43:17,060 Because, now, I've only got-- 949 00:43:17,060 --> 00:43:21,698 see, each of these carbon atoms only needs two sigma bonds. 950 00:43:21,698 --> 00:43:24,167 One to the hydrogen and one to the other carbon. 951 00:43:24,167 --> 00:43:26,803 So it's only going to grab one-- 952 00:43:26,803 --> 00:43:28,204 it's only going to hybridize-- 953 00:43:28,204 --> 00:43:30,006 to make those two equivalent signal bonds, 954 00:43:30,006 --> 00:43:32,709 it's only going to hybridize with one of the p electrons. 955 00:43:32,709 --> 00:43:34,711 So that's sp. 956 00:43:34,711 --> 00:43:36,212 That's sp hybridization. 957 00:43:36,212 --> 00:43:38,915 But, notice, that in C2H2, it-- you know, 958 00:43:38,915 --> 00:43:45,622 now, I've got 2p orbitals left over on each carbon atom. 959 00:43:45,622 --> 00:43:49,859 And so you can imagine that with these 2p orbitals, 960 00:43:49,859 --> 00:43:51,761 well, you know this already, right. 961 00:43:51,761 --> 00:43:54,230 When-- when we talked about p orbitals, 962 00:43:54,230 --> 00:43:57,233 we talked about how, you know, you 963 00:43:57,233 --> 00:43:58,935 might-- you know, you've got this, right. 964 00:43:58,935 --> 00:43:59,402 Awe. 965 00:44:01,938 --> 00:44:02,405 OK. 966 00:44:02,405 --> 00:44:04,007 That's supposed to come like out of the plane 967 00:44:04,007 --> 00:44:04,774 and into the plane. 968 00:44:04,774 --> 00:44:06,042 They're orthogonal. 969 00:44:06,042 --> 00:44:07,043 They're orthogonal. 970 00:44:07,043 --> 00:44:07,510 Right. 971 00:44:07,510 --> 00:44:14,784 And so-- so two of them are coming at the other atom. 972 00:44:14,784 --> 00:44:17,687 One is like this, and the other's like that. 973 00:44:17,687 --> 00:44:19,789 And then the other atom is one like this and one-- 974 00:44:19,789 --> 00:44:22,525 well, it might not at first, but then when it sees those, 975 00:44:22,525 --> 00:44:23,760 it's like, hey, wait a second. 976 00:44:23,760 --> 00:44:27,697 If I do this, we can pi bond. 977 00:44:27,697 --> 00:44:28,231 Right. 978 00:44:28,231 --> 00:44:30,333 The other ones are like this, and they pi bond, 979 00:44:30,333 --> 00:44:33,236 and so you get a carbon carbon triple bond. 980 00:44:33,236 --> 00:44:35,038 You get a carbon carbon triple bond 981 00:44:35,038 --> 00:44:38,908 for a C2H2 with sp hybridization. 982 00:44:38,908 --> 00:44:40,610 Now, it's not-- oh, there it is. 983 00:44:40,610 --> 00:44:41,077 Right. 984 00:44:41,077 --> 00:44:41,911 OK. 985 00:44:41,911 --> 00:44:44,280 Forms pipe bond network, forms sigma bond network. 986 00:44:44,280 --> 00:44:46,449 It's not just carbon that hybridizes. 987 00:44:46,449 --> 00:44:49,285 It's not-- carbon is a classic example. 988 00:44:49,285 --> 00:44:56,559 But, you know, if you look at BeH2, it's the same thing. 989 00:44:56,559 --> 00:44:57,827 BeH2. 990 00:44:57,827 --> 00:45:03,199 Well, Be, Be starts with an un-- 991 00:45:06,002 --> 00:45:07,937 can I raise this up? 992 00:45:07,937 --> 00:45:11,708 Be starts with orbitals that don't 993 00:45:11,708 --> 00:45:15,111 look like they're going to give me the equivalent two sigma 994 00:45:15,111 --> 00:45:15,812 bonds. 995 00:45:15,812 --> 00:45:21,751 Be starts with these as electrons filled. 996 00:45:21,751 --> 00:45:24,020 Right. 997 00:45:24,020 --> 00:45:28,658 But if Be had something more like this, 998 00:45:28,658 --> 00:45:33,229 if it had an sp electron in each of those orbitals, 999 00:45:33,229 --> 00:45:39,502 well, now, when I see the two h orbitals, the two 1 SH orbitals 1000 00:45:39,502 --> 00:45:42,772 coming at me, I can form those equivalent bonds. 1001 00:45:42,772 --> 00:45:45,241 So BeH2 will also hybridize [INAUDIBLE] 1002 00:45:45,241 --> 00:45:47,510 to make that molecule. 1003 00:45:47,510 --> 00:45:49,145 And all sorts of other things. 1004 00:45:49,145 --> 00:45:51,347 The deal orbitals can get in on the action. 1005 00:45:51,347 --> 00:45:51,881 All right. 1006 00:45:51,881 --> 00:45:53,983 So here's SF6, which we talked about. 1007 00:45:53,983 --> 00:45:57,520 We drew this Lewis structure. 1008 00:45:57,520 --> 00:45:59,989 Took a long time to draw those lone pairs. 1009 00:45:59,989 --> 00:46:02,859 But, now, you know that the way this actually 1010 00:46:02,859 --> 00:46:05,428 works because these are equivalent bonds. 1011 00:46:05,428 --> 00:46:09,365 So the only way this can work is if I form hybrid orbitals. 1012 00:46:09,365 --> 00:46:09,899 Right. 1013 00:46:09,899 --> 00:46:10,366 Right. 1014 00:46:10,366 --> 00:46:12,769 But they didn't have to be equivalent bonds 1015 00:46:12,769 --> 00:46:15,271 until we learned about VSEPR. 1016 00:46:15,271 --> 00:46:19,242 And it said, no, I want to maximize my separation 1017 00:46:19,242 --> 00:46:20,443 to minimize repulsions. 1018 00:46:20,443 --> 00:46:24,080 And so then we know that if they're equivalent bonds, 1019 00:46:24,080 --> 00:46:26,816 the energy of the system will be lower. 1020 00:46:26,816 --> 00:46:27,917 Right. 1021 00:46:27,917 --> 00:46:29,919 And so that-- that's-- 1022 00:46:29,919 --> 00:46:32,655 you know, that's going to have to take some d orbitals 1023 00:46:32,655 --> 00:46:35,158 and create these hybrid orbitals. 1024 00:46:35,158 --> 00:46:36,159 Look, they're beautiful. 1025 00:46:36,159 --> 00:46:39,929 Because, now, this thing from the sulfur, this thing can say, 1026 00:46:39,929 --> 00:46:43,266 hey, I can take six of you, and I can be equivalent bonding 1027 00:46:43,266 --> 00:46:44,200 to all of you. 1028 00:46:44,200 --> 00:46:46,402 That's what hybridization is. 1029 00:46:46,402 --> 00:46:47,103 OK. 1030 00:46:47,103 --> 00:46:48,304 It's written right up there. 1031 00:46:48,304 --> 00:46:50,540 We're just keeping on saying the same thing. 1032 00:46:50,540 --> 00:46:51,107 OK. 1033 00:46:51,107 --> 00:46:56,112 Now, I think that I'm sorry-- 1034 00:46:56,112 --> 00:46:57,547 I got very excited about the water 1035 00:46:57,547 --> 00:47:00,383 so I have to throw some T-shirts out. 1036 00:47:00,383 --> 00:47:02,652 And, now, where do I-- where do I-- 1037 00:47:02,652 --> 00:47:03,119 OK. 1038 00:47:03,119 --> 00:47:04,754 I don't go there. 1039 00:47:04,754 --> 00:47:06,823 I don't go there. 1040 00:47:06,823 --> 00:47:12,228 I got to go back there, and back there. 1041 00:47:12,228 --> 00:47:13,830 Oh, that's very loud. 1042 00:47:13,830 --> 00:47:14,597 OK. 1043 00:47:14,597 --> 00:47:16,032 And right there. 1044 00:47:16,032 --> 00:47:19,402 And right there. 1045 00:47:19,402 --> 00:47:21,571 See you guys on Friday.