1 00:00:17,416 --> 00:00:20,419 I want to start right where we left off, 2 00:00:20,419 --> 00:00:24,857 which is in filling atoms, filling electrons into atoms. 3 00:00:24,857 --> 00:00:30,796 We've done a lot of work to know what it is that we're filling. 4 00:00:30,796 --> 00:00:34,066 We had to go all the way to quantum 5 00:00:34,066 --> 00:00:38,337 to know what orbitals are, not just orbits. 6 00:00:38,337 --> 00:00:39,872 Right. 7 00:00:39,872 --> 00:00:44,910 And we talked about the four quantum numbers, right? 8 00:00:44,910 --> 00:00:48,781 And so now we're going to use those, 9 00:00:48,781 --> 00:00:52,518 and we're going to use the exclusion principle from Pauli 10 00:00:52,518 --> 00:00:54,053 and a few other things. 11 00:00:54,053 --> 00:00:56,622 And we're going to fill electrons into atoms. 12 00:00:56,622 --> 00:00:59,658 So this is where we left off on Monday. 13 00:00:59,658 --> 00:01:00,793 There they are, right? 14 00:01:00,793 --> 00:01:04,997 Remember, you know, as I said on Monday, 15 00:01:04,997 --> 00:01:08,467 if we only had Bohr, what we would have is the left hand 16 00:01:08,467 --> 00:01:11,070 side here, n equals 1. 17 00:01:11,070 --> 00:01:14,306 We would have just have n equals 1, 2, 3, 4, 5, 18 00:01:14,306 --> 00:01:18,811 but we wouldn't have any of this variation of l, right, 19 00:01:18,811 --> 00:01:23,049 like the p electrons, the d electrons. 20 00:01:23,049 --> 00:01:25,283 That differentiation came in when 21 00:01:25,283 --> 00:01:29,321 we solved the equations of quantum mechanics, right, 22 00:01:29,321 --> 00:01:36,495 for an electron in feeling the potential of the proton. 23 00:01:36,495 --> 00:01:38,229 And then the other thing that happens 24 00:01:38,229 --> 00:01:40,933 is these things don't line up necessarily 25 00:01:40,933 --> 00:01:43,335 exactly how you might imagine, because there 26 00:01:43,335 --> 00:01:47,773 are complicated effects, right? 27 00:01:47,773 --> 00:01:51,509 It's not just a naive feeling. 28 00:01:51,509 --> 00:01:54,880 Instead there's these effects like shielding. 29 00:01:54,880 --> 00:01:57,883 Right, so electrons all the way out here in an atom, 30 00:01:57,883 --> 00:02:00,419 they don't necessarily see all the protons. 31 00:02:00,419 --> 00:02:02,621 They're shielded. 32 00:02:02,621 --> 00:02:05,791 And then to make matters even more complicated, 33 00:02:05,791 --> 00:02:11,163 these orbitals can wiggle in with nodes, right? 34 00:02:11,163 --> 00:02:12,731 This is what we did Monday, with nodes 35 00:02:12,731 --> 00:02:16,268 all the way in so they can see-- some of these orbitals 36 00:02:16,268 --> 00:02:21,107 have a little bit of them that see the protons up close. 37 00:02:21,107 --> 00:02:23,175 So we showed that with 2s. 38 00:02:23,175 --> 00:02:25,010 That's called orbital penetration. 39 00:02:25,010 --> 00:02:28,147 And that's why these things split up. 40 00:02:28,147 --> 00:02:31,450 They have the same principle quantum number, n is 2, 41 00:02:31,450 --> 00:02:34,019 but this has a lower energy than the 2p. 42 00:02:37,823 --> 00:02:43,028 But how is the electron moving within this orbital? 43 00:02:43,028 --> 00:02:44,763 No. 44 00:02:44,763 --> 00:02:45,297 It's not. 45 00:02:45,297 --> 00:02:48,300 That's a classical way of thinking, right? 46 00:02:48,300 --> 00:02:50,668 And it's so hard to stop thinking that way. 47 00:02:50,668 --> 00:02:52,204 I know we want to think that way. 48 00:02:52,204 --> 00:02:52,905 But it's not. 49 00:02:52,905 --> 00:02:56,575 An electron is being in its orbital, 50 00:02:56,575 --> 00:03:00,312 because an orbital is a probability distribution. 51 00:03:00,312 --> 00:03:01,480 All right? 52 00:03:01,480 --> 00:03:04,316 So the electron, all we know from that orbital 53 00:03:04,316 --> 00:03:07,052 is that the electron has a probability of being here 54 00:03:07,052 --> 00:03:10,422 sometimes and a probability of being there other times. 55 00:03:10,422 --> 00:03:11,423 That's what it tells us. 56 00:03:11,423 --> 00:03:13,792 So we know that in that 2s orbital, sometimes 57 00:03:13,792 --> 00:03:17,596 it's really, really close to those protons, right? 58 00:03:17,596 --> 00:03:19,431 That was that orbital penetration, the peak 59 00:03:19,431 --> 00:03:21,066 that you saw on Monday. 60 00:03:21,066 --> 00:03:23,035 All right, so with all that knowledge just kind 61 00:03:23,035 --> 00:03:24,570 of getting us back in the mood here 62 00:03:24,570 --> 00:03:27,673 and our quantum numbers and our Pauli exclusion, 63 00:03:27,673 --> 00:03:29,508 we're ready to fill. 64 00:03:29,508 --> 00:03:33,879 And the way that we're going to start 65 00:03:33,879 --> 00:03:39,718 is the way that most chemistry textbooks would start, 66 00:03:39,718 --> 00:03:43,689 which is with a very simple rule, all right, 67 00:03:43,689 --> 00:03:45,991 called the aufbau principle. 68 00:03:45,991 --> 00:03:55,267 And aufbau means-- so aufbau means filling up in German. 69 00:03:55,267 --> 00:04:00,439 And basically the idea is that you fill-- 70 00:04:03,108 --> 00:04:10,916 you fill from the lowest levels, the lowest. 71 00:04:10,916 --> 00:04:12,751 Those are also the ground state. 72 00:04:12,751 --> 00:04:15,487 Right, the ground state would be the lowest, right? 73 00:04:15,487 --> 00:04:25,297 That's the lowest energy, lowest levels, ground state level, 74 00:04:25,297 --> 00:04:28,100 energy, and up. 75 00:04:28,100 --> 00:04:29,201 OK. 76 00:04:29,201 --> 00:04:35,007 And you use what is called the n plus l rule. 77 00:04:37,509 --> 00:04:46,418 The n plus l rule means that the ordering, the ordering 78 00:04:46,418 --> 00:04:50,322 of the orbital energies-- 79 00:04:50,322 --> 00:04:58,264 orbital energies-- and let's get a little more space here OK. 80 00:04:58,264 --> 00:05:02,434 The ordering of the orbital energies 81 00:05:02,434 --> 00:05:13,445 increases with increasing n plus l. 82 00:05:13,445 --> 00:05:16,181 All right, you fill from the lowest energy up. 83 00:05:16,181 --> 00:05:18,517 So as my n plus l, those are the-- 84 00:05:18,517 --> 00:05:20,686 remember, that's the shape. 85 00:05:20,686 --> 00:05:23,789 This is sort of related to the distance from the nucleus. 86 00:05:23,789 --> 00:05:25,324 This is the principle quantum number. 87 00:05:25,324 --> 00:05:27,159 This is related to the shape of the orbital. 88 00:05:27,159 --> 00:05:31,463 Right l, and as that number increases, the energy, 89 00:05:31,463 --> 00:05:32,331 that's how you fill. 90 00:05:32,331 --> 00:05:37,169 Oh, but there's the case where it might be the same. 91 00:05:37,169 --> 00:05:41,073 All right, so we have to have another point here, 92 00:05:41,073 --> 00:05:45,344 which is when two orbitals-- 93 00:05:45,344 --> 00:05:46,578 I did it again. 94 00:05:46,578 --> 00:05:48,213 I forgot my r. 95 00:05:48,213 --> 00:06:02,227 Two orbitals have the same n plus l, then the lower n 96 00:06:02,227 --> 00:06:06,598 has lower e. 97 00:06:06,598 --> 00:06:09,868 OK, this is called the n plus l rule, 98 00:06:09,868 --> 00:06:11,337 but rules are made to be broken. 99 00:06:11,337 --> 00:06:17,609 So as we're going to see, this is actually really only true 100 00:06:17,609 --> 00:06:21,246 maybe 80% of the time. 101 00:06:21,246 --> 00:06:23,882 But we're going to use it, because it is a good framework, 102 00:06:23,882 --> 00:06:25,751 and it captures-- 103 00:06:25,751 --> 00:06:29,755 it gives us a way to start thinking about electron 104 00:06:29,755 --> 00:06:30,789 occupation and atoms. 105 00:06:30,789 --> 00:06:33,692 And so if you take these two points, this filling up 106 00:06:33,692 --> 00:06:35,894 and the ordering of how you fill things, 107 00:06:35,894 --> 00:06:38,764 then you can draw this as a very simple picture. 108 00:06:38,764 --> 00:06:40,899 This is from the textbook Averill, 109 00:06:40,899 --> 00:06:44,403 right, where what you do is you follow the arrows. 110 00:06:44,403 --> 00:06:48,140 OK, so you go this arrow, I'm filling 1s, this arrow, 111 00:06:48,140 --> 00:06:49,641 then I go to 2s. 112 00:06:49,641 --> 00:06:51,076 Right, it's not going anywhere. 113 00:06:51,076 --> 00:06:53,712 So you go there, and you keep following. 114 00:06:57,182 --> 00:07:03,088 OK, so 2s, 2p, so you'd fill 1s, 2s, then 2p, right, 115 00:07:03,088 --> 00:07:06,191 because of the n plus l rules is in effect. 116 00:07:06,191 --> 00:07:08,460 And then, OK, 3s. 117 00:07:08,460 --> 00:07:10,195 n is 3, l is 0. 118 00:07:10,195 --> 00:07:11,930 That's n plus 2 is 3. 119 00:07:11,930 --> 00:07:17,035 2p, 2p, n is 2, l is 1, same value. 120 00:07:17,035 --> 00:07:18,737 But now I go to this one here, and when 121 00:07:18,737 --> 00:07:21,807 they have the same value, the lower n has lower energy. 122 00:07:21,807 --> 00:07:24,443 Lower n filled first. 123 00:07:24,443 --> 00:07:26,178 Filled first, because the ordering 124 00:07:26,178 --> 00:07:29,214 is to go from lowest energy up. 125 00:07:29,214 --> 00:07:31,016 OK. 126 00:07:31,016 --> 00:07:34,920 All right, so that's our rule, which will be broken. 127 00:07:37,589 --> 00:07:40,659 Now, how does this look? 128 00:07:40,659 --> 00:07:44,029 Well, if we do this, we're going to get a little notation here 129 00:07:44,029 --> 00:07:46,832 and that's important, if we do this, 130 00:07:46,832 --> 00:07:51,503 and we just do a few atoms here, so for hydrogen, right, 131 00:07:51,503 --> 00:07:54,072 so for hydrogen we'd have-- 132 00:07:54,072 --> 00:08:00,846 that's the 1s orbital, and we're putting in one electron in it. 133 00:08:00,846 --> 00:08:02,314 Now, the notation here is something 134 00:08:02,314 --> 00:08:03,615 that we're going to use a lot. 135 00:08:03,615 --> 00:08:07,252 So let me explain this. 136 00:08:07,252 --> 00:08:09,788 This is n. 137 00:08:09,788 --> 00:08:11,723 This is l. 138 00:08:11,723 --> 00:08:16,962 That's the l in, what, spectroscopic notation, right? 139 00:08:16,962 --> 00:08:20,265 Remember we talked about that Monday, right, s, p, d. 140 00:08:20,265 --> 00:08:22,267 OK. 141 00:08:22,267 --> 00:08:28,006 And then this is the number of electrons. 142 00:08:28,006 --> 00:08:30,442 And so if we keep going with this notation, 143 00:08:30,442 --> 00:08:34,446 then in the case of helium, so for helium 144 00:08:34,446 --> 00:08:39,985 you would have 1s2, because I fill a second electron 145 00:08:39,985 --> 00:08:41,986 into the 1s orbital. 146 00:08:41,986 --> 00:08:44,656 Now, this is where Pauli comes in. 147 00:08:44,656 --> 00:08:46,558 Right, Paul said, OK, enough. 148 00:08:46,558 --> 00:08:50,028 You're done with that orbital, because I've got two electrons. 149 00:08:50,028 --> 00:08:52,831 They do have different quantum numbers. 150 00:08:52,831 --> 00:08:54,665 They've got the same n. 151 00:08:54,665 --> 00:08:57,402 Right, they've got the same l. 152 00:08:57,402 --> 00:09:00,405 Their m sub l's are the same because there 153 00:09:00,405 --> 00:09:02,040 is no range here for s, right. 154 00:09:02,040 --> 00:09:05,210 Remember m sub l for s can only be, you know, zero. 155 00:09:05,210 --> 00:09:10,015 But they have different spins, up and down. 156 00:09:10,015 --> 00:09:13,318 And so sometimes, what is also really useful, 157 00:09:13,318 --> 00:09:15,554 and we'll go back and forth between these pictures, 158 00:09:15,554 --> 00:09:19,157 is you go back to what we drew, you know, with the Bohr model, 159 00:09:19,157 --> 00:09:22,861 where we draw this in terms of energy levels. 160 00:09:22,861 --> 00:09:25,597 And so if you drew this in terms of energy levels, 161 00:09:25,597 --> 00:09:26,798 this is what'd you see. 162 00:09:26,798 --> 00:09:29,701 So you'd have like energy. 163 00:09:29,701 --> 00:09:31,703 And remember, in the hydrogen atom, 164 00:09:31,703 --> 00:09:34,439 this is minus 13.6 electron volts. 165 00:09:34,439 --> 00:09:36,708 And so if you wanted to draw this in this way, 166 00:09:36,708 --> 00:09:39,244 you would say, OK, there is one electron there, 167 00:09:39,244 --> 00:09:41,947 and we'll-- remember, we said you can draw electron spin with 168 00:09:41,947 --> 00:09:43,582 arrows. 169 00:09:43,582 --> 00:09:47,886 Right, whereas here, if we drew this, then we draw-- 170 00:09:47,886 --> 00:09:49,721 I'm not putting the energy there. 171 00:09:49,721 --> 00:09:54,359 We don't know it, because Bohr 13.6 good for hydrogen. Right, 172 00:09:54,359 --> 00:09:55,193 but here-- 173 00:09:55,193 --> 00:09:58,463 oh, and by the way, this would be the 1s orbital. 174 00:09:58,463 --> 00:10:00,465 This would be the 1s orbital. 175 00:10:00,465 --> 00:10:04,570 But in this case, I've got two electrons, one up, one down. 176 00:10:07,472 --> 00:10:09,708 And now, Pauli says you're done. 177 00:10:09,708 --> 00:10:10,208 All right. 178 00:10:10,208 --> 00:10:18,283 And so if you go to lithium, then you have 1s2 2s1. 179 00:10:18,283 --> 00:10:21,587 And so if you drew this in terms of an energy diagram, 180 00:10:21,587 --> 00:10:26,024 you'd have the 1s, and we're putting that, 181 00:10:26,024 --> 00:10:28,927 and then you have the 2s somewhere up higher 182 00:10:28,927 --> 00:10:31,296 where we put one electron. 183 00:10:31,296 --> 00:10:35,133 Those are-- that's how you would see these atoms in terms 184 00:10:35,133 --> 00:10:38,003 of the filling of the electrons into their orbitals. 185 00:10:38,003 --> 00:10:38,870 Right. 186 00:10:38,870 --> 00:10:41,406 OK, good. 187 00:10:41,406 --> 00:10:44,109 Now, OK, let's keep going. 188 00:10:44,109 --> 00:10:46,378 So what we'll do is we'll do this here. 189 00:10:46,378 --> 00:10:47,245 So let's see. 190 00:10:47,245 --> 00:10:53,318 So beryllium would be 1s2 2s2. 191 00:10:53,318 --> 00:11:03,261 And boron would be 1s2 2s2 2p1. 192 00:11:03,261 --> 00:11:05,130 OK, this is looking good here, right? 193 00:11:05,130 --> 00:11:08,033 I'm really following aufbau now. 194 00:11:08,033 --> 00:11:11,269 Oh, I went that way, then I went that way, 195 00:11:11,269 --> 00:11:12,904 and then I went up here, and I started 196 00:11:12,904 --> 00:11:15,807 on this arrow, which is just a way, graphically, of showing 197 00:11:15,807 --> 00:11:17,175 those rules. 198 00:11:17,175 --> 00:11:19,044 Good. 199 00:11:19,044 --> 00:11:23,281 Now, we get to carbon. 200 00:11:23,281 --> 00:11:25,984 And now we have to think about this, right, 201 00:11:25,984 --> 00:11:33,925 because for carbon, I've got 1s2 2s2 2p2. 202 00:11:33,925 --> 00:11:35,727 That is correct. 203 00:11:35,727 --> 00:11:36,261 All right. 204 00:11:36,261 --> 00:11:39,631 But if I think about this in terms of the energy, 205 00:11:39,631 --> 00:11:48,807 1s2, 2s, right, well we know from before, right, we 206 00:11:48,807 --> 00:11:52,377 know from before, like 2p. 207 00:11:52,377 --> 00:11:53,111 Where is 2p? 208 00:11:53,111 --> 00:11:53,945 There it is. 209 00:11:53,945 --> 00:11:57,015 It's got six electrons that it can take. 210 00:11:57,015 --> 00:12:02,954 Because now m sub l can vary from minus 1, 0, plus 1. 211 00:12:02,954 --> 00:12:05,924 Remember, that corresponded to the three 212 00:12:05,924 --> 00:12:09,728 different orientations of the p orbital. 213 00:12:09,728 --> 00:12:11,129 OK. 214 00:12:11,129 --> 00:12:13,699 But that means that I've got three, 215 00:12:13,699 --> 00:12:16,935 so I can fill this with 2, 2, and then 216 00:12:16,935 --> 00:12:19,037 the question is, what do I do? 217 00:12:19,037 --> 00:12:20,739 I don't know what to do. 218 00:12:20,739 --> 00:12:22,407 Do I do this? 219 00:12:22,407 --> 00:12:23,775 Is that right? 220 00:12:23,775 --> 00:12:25,343 No, somebody says. 221 00:12:25,343 --> 00:12:27,713 And that person knows that the answer is no, 222 00:12:27,713 --> 00:12:29,414 because that person knows Hund. 223 00:12:29,414 --> 00:12:30,348 Where's Hund? 224 00:12:30,348 --> 00:12:32,784 There he is. 225 00:12:32,784 --> 00:12:34,886 Would have been more dramatic had he appeared, 226 00:12:34,886 --> 00:12:37,122 but there he is, because Hund came up 227 00:12:37,122 --> 00:12:42,427 with another rule, which also is broken, sometimes. 228 00:12:42,427 --> 00:12:44,596 Not as much as aufbau. 229 00:12:44,596 --> 00:12:52,270 You know, so Hund said look, when you have a case like this, 230 00:12:52,270 --> 00:13:00,445 electrons in the same p, so the same like orbital, sub shell. 231 00:13:00,445 --> 00:13:05,016 OK, it's not the same sub shell, but it's the same n 2p. 232 00:13:05,016 --> 00:13:05,884 Let's draw that. 233 00:13:05,884 --> 00:13:07,285 It is the same sub shell. 234 00:13:07,285 --> 00:13:08,754 I'm saying opposite things. 235 00:13:08,754 --> 00:13:12,157 2p, 2p. 236 00:13:12,157 --> 00:13:14,259 Shell, sub shell. 237 00:13:14,259 --> 00:13:16,294 But there are different possibilities, 238 00:13:16,294 --> 00:13:18,563 and how you fill them according to Hund 239 00:13:18,563 --> 00:13:22,200 is you maximize what's called the multiplicity, which 240 00:13:22,200 --> 00:13:24,803 means that you want the electrons to come 241 00:13:24,803 --> 00:13:29,307 in with the same spin in different orbitals, 242 00:13:29,307 --> 00:13:32,010 in different p orbitals. 243 00:13:32,010 --> 00:13:33,411 That's how you fill them. 244 00:13:33,411 --> 00:13:34,179 Why? 245 00:13:34,179 --> 00:13:39,184 Well, that has to do with more quantum mechanics, 246 00:13:39,184 --> 00:13:41,686 and it has to do with something called exchange energy that's 247 00:13:41,686 --> 00:13:43,955 not part of what you need to know about. 248 00:13:43,955 --> 00:13:46,324 And I'm not going to teach it here. 249 00:13:46,324 --> 00:13:48,860 But you know, you can think about it simply 250 00:13:48,860 --> 00:13:51,863 as the electrons want to spread out, 251 00:13:51,863 --> 00:13:55,033 because they repel each other in the same orbital. 252 00:13:55,033 --> 00:13:55,967 Right. 253 00:13:55,967 --> 00:13:58,069 They want a lot of things, electrons. 254 00:13:58,069 --> 00:14:01,039 They want to be close to protons. 255 00:14:01,039 --> 00:14:04,709 But they want to be kind of not close to each other. 256 00:14:04,709 --> 00:14:06,344 They need their space. 257 00:14:06,344 --> 00:14:07,445 That's not a lot of things. 258 00:14:07,445 --> 00:14:08,513 It's two things. 259 00:14:08,513 --> 00:14:10,048 But that's what they want. 260 00:14:10,048 --> 00:14:13,852 And this allows them to maximize that and lower their energy. 261 00:14:13,852 --> 00:14:15,253 And remember, lowering your energy 262 00:14:15,253 --> 00:14:17,856 means happiness for electrons. 263 00:14:17,856 --> 00:14:20,992 So this is the preferred way to fill, right? 264 00:14:20,992 --> 00:14:24,229 And that's what Hund's rule tells us. 265 00:14:24,229 --> 00:14:28,333 Now, if you go to silicon, and you say, 266 00:14:28,333 --> 00:14:30,001 well, OK, what does silicon look like? 267 00:14:33,104 --> 00:14:34,873 All right, I'm going to put silicon-- 268 00:14:34,873 --> 00:14:37,275 no, don't do that. 269 00:14:37,275 --> 00:14:40,111 I'm going to put silicon right underneath carbon, 270 00:14:40,111 --> 00:14:42,480 because I think it's an interesting comparison. 271 00:14:42,480 --> 00:14:45,350 All right, so silicon is OK-- 272 00:14:45,350 --> 00:14:50,388 1s2 2s2 2p6. 273 00:14:50,388 --> 00:14:52,090 They're all filled. 274 00:14:52,090 --> 00:14:58,763 Right, and then you go to 3s2 and you go to 3p2. 275 00:14:58,763 --> 00:15:00,632 And this looks very different than carbon, 276 00:15:00,632 --> 00:15:03,902 but actually, you can abbreviate the notation, 277 00:15:03,902 --> 00:15:09,574 and we very often do in these filling notation, 278 00:15:09,574 --> 00:15:10,675 and we do it this way. 279 00:15:10,675 --> 00:15:13,411 We say, well, this has a neon core. 280 00:15:13,411 --> 00:15:16,581 So you go to the nearest noble gas, 281 00:15:16,581 --> 00:15:18,950 not with more electrons, because they're not there, 282 00:15:18,950 --> 00:15:20,585 with less electrons. 283 00:15:20,585 --> 00:15:24,055 You go to the nearest noble gas, and say well, OK, that's 284 00:15:24,055 --> 00:15:25,490 basically neon. 285 00:15:25,490 --> 00:15:27,959 All right, this is neon. 286 00:15:27,959 --> 00:15:31,796 And so you can write the notation is this-- 287 00:15:31,796 --> 00:15:35,500 it's the same atom, just a slightly abbreviated way 288 00:15:35,500 --> 00:15:37,969 of writing it, where I would write, OK, this is 289 00:15:37,969 --> 00:15:43,341 a neon core with 3s2 and 3p2. 290 00:15:43,341 --> 00:15:47,445 Well, you can write that with a helium core, 2s2 2p2. 291 00:15:47,445 --> 00:15:51,516 And what happens is you wind up having a nice distinction here, 292 00:15:51,516 --> 00:15:55,086 because these are core electrons. 293 00:15:55,086 --> 00:15:57,088 Remember, we're filling electrons here. 294 00:15:57,088 --> 00:15:59,824 That's electrons. 295 00:15:59,824 --> 00:16:05,096 And these are called valence electrons, 296 00:16:05,096 --> 00:16:10,535 and we'll be talking about valence chemistry 297 00:16:10,535 --> 00:16:14,572 for the whole semester and what these valence electrons do, 298 00:16:14,572 --> 00:16:16,975 right? 299 00:16:16,975 --> 00:16:18,944 And in fact, these valence electrons, 300 00:16:18,944 --> 00:16:23,281 these ones on the outside closest to the out-- 301 00:16:23,281 --> 00:16:25,917 furthest away, these are the ones 302 00:16:25,917 --> 00:16:29,287 that have all of the chemistry that we care 303 00:16:29,287 --> 00:16:33,224 about in this class, chemistry. 304 00:16:33,224 --> 00:16:38,229 It's so important that I went all caps. 305 00:16:38,229 --> 00:16:41,499 I'm not shouting, but I went all caps. 306 00:16:41,499 --> 00:16:44,869 Whereas the core electrons are kind of mostly inert. 307 00:16:44,869 --> 00:16:50,308 They're mostly inert, chemically inert. 308 00:16:50,308 --> 00:16:55,513 OK, and so sometimes it's very useful 309 00:16:55,513 --> 00:16:59,584 to write the notation this way to see 310 00:16:59,584 --> 00:17:02,587 what do you got in the valence, what's going on? 311 00:17:02,587 --> 00:17:04,155 Right, what does this valence-- 312 00:17:04,155 --> 00:17:06,257 because then you start to see similarities. 313 00:17:06,257 --> 00:17:11,997 The valence for lithium and the valence for sodium 314 00:17:11,997 --> 00:17:13,865 look really similar. 315 00:17:13,865 --> 00:17:15,066 There's an outer s electron. 316 00:17:15,066 --> 00:17:17,335 That's the quantum number, the principle quantum number 317 00:17:17,335 --> 00:17:18,036 is different. 318 00:17:18,036 --> 00:17:19,503 But the valence looks very similar, 319 00:17:19,503 --> 00:17:21,906 one electron in an s orbital. 320 00:17:21,906 --> 00:17:25,143 And that allows us to think intuitively 321 00:17:25,143 --> 00:17:27,712 about similarities between elements, 322 00:17:27,712 --> 00:17:29,280 because if they have the same valence, 323 00:17:29,280 --> 00:17:33,918 and the valence is responsible, not same, but similar, 324 00:17:33,918 --> 00:17:36,921 similar shapes of orbitals, different principal 325 00:17:36,921 --> 00:17:40,025 numbers, but if that's similar, then maybe the chemistry 326 00:17:40,025 --> 00:17:42,660 those elements do is also similar. 327 00:17:42,660 --> 00:17:45,063 This is a helpful way to think about it. 328 00:17:45,063 --> 00:17:46,464 OK. 329 00:17:46,464 --> 00:17:48,933 I told you that rules are meant to be broken, 330 00:17:48,933 --> 00:17:52,003 especially when we're talking about n plus l, 331 00:17:52,003 --> 00:17:53,171 and it happens all the time. 332 00:17:53,171 --> 00:17:57,675 And there's two main reasons or important reasons, 333 00:17:57,675 --> 00:18:00,211 and then there's a whole bunch of other very complicated ones, 334 00:18:00,211 --> 00:18:02,313 that two I want you to know about, 335 00:18:02,313 --> 00:18:05,183 which are exceptions to this aufbau filling, 336 00:18:05,183 --> 00:18:07,852 OK, which are exceptions to that, 337 00:18:07,852 --> 00:18:09,921 come in the following situations. 338 00:18:09,921 --> 00:18:12,924 That you get stability-- 339 00:18:12,924 --> 00:18:13,825 you get stability. 340 00:18:13,825 --> 00:18:16,094 That means lower energy for the whole system. 341 00:18:16,094 --> 00:18:18,096 The system lowers its energy and can 342 00:18:18,096 --> 00:18:23,768 be more stable when either an orbital is fully filled-- 343 00:18:23,768 --> 00:18:26,704 there it is, ns2, np6, nd10. 344 00:18:26,704 --> 00:18:28,706 You know those are fully filled, because that's 345 00:18:28,706 --> 00:18:32,043 how many elections you can put in each one, or half filled 346 00:18:32,043 --> 00:18:33,144 exactly. 347 00:18:33,144 --> 00:18:36,681 And so that's why in chromium if you predict with aufbau, 348 00:18:36,681 --> 00:18:39,417 you would get 4s2 3d4, but actually you 349 00:18:39,417 --> 00:18:43,421 get 4s1 3d5, because you can half fill both of those, 350 00:18:43,421 --> 00:18:45,890 and that adds to the stability. 351 00:18:45,890 --> 00:18:48,793 In copper, the predicted one would be 4s2 3d9. 352 00:18:48,793 --> 00:18:53,098 But actually what you see is a fully filled d shell, which 353 00:18:53,098 --> 00:18:56,234 adds to stability and a half filled s shell. 354 00:18:56,234 --> 00:18:58,269 So it's willing to make this trade off 355 00:18:58,269 --> 00:19:00,371 of a fully filled s show for half filled. 356 00:19:00,371 --> 00:19:02,907 That's not a big trade off to get the d, fully filled. 357 00:19:02,907 --> 00:19:06,010 OK, now there's more complicated effects, 358 00:19:06,010 --> 00:19:12,650 all sorts of effects that also lead to violations 359 00:19:12,650 --> 00:19:14,119 of the n plus l rule. 360 00:19:14,119 --> 00:19:17,455 I really hesitate to call it a rule, given that, you know, 361 00:19:17,455 --> 00:19:20,458 there's a lot of examples where it's not 362 00:19:20,458 --> 00:19:22,827 about the half filling or the full filling. 363 00:19:22,827 --> 00:19:25,530 It's about complicated interactions 364 00:19:25,530 --> 00:19:28,099 that have to do sometimes, all the way with things 365 00:19:28,099 --> 00:19:31,402 like relativity, relativistic effects, literally, 366 00:19:31,402 --> 00:19:38,209 of these electrons, which will not be on any quiz or exam, 367 00:19:38,209 --> 00:19:41,579 with also the complexities that happen with orbital penetration 368 00:19:41,579 --> 00:19:43,314 as you add more and more electrons 369 00:19:43,314 --> 00:19:47,218 and the levels are kind of closer together. 370 00:19:47,218 --> 00:19:51,055 They're a lot harder to see clearly separate energies 371 00:19:51,055 --> 00:19:52,857 than in the first two, three rows, 372 00:19:52,857 --> 00:19:54,492 as you go down in the periodic table, 373 00:19:54,492 --> 00:19:56,294 those levels are closer and closer together. 374 00:19:56,294 --> 00:19:57,695 So anomalies happen. 375 00:19:57,695 --> 00:19:58,696 But they're not really-- 376 00:19:58,696 --> 00:20:01,065 I'm not sure we should call them anomalies, because these 377 00:20:01,065 --> 00:20:04,702 are all exceptions to aufbau. 378 00:20:04,702 --> 00:20:06,604 So like I said, I want you to know aufbau, 379 00:20:06,604 --> 00:20:08,039 because it's a great way to start, 380 00:20:08,039 --> 00:20:12,577 but I also want you to know that sometimes things switch around 381 00:20:12,577 --> 00:20:15,513 because of the effects that we've been talking about. 382 00:20:15,513 --> 00:20:19,250 I don't expect you to memorize all the exceptions to aufbau, 383 00:20:19,250 --> 00:20:20,351 OK? 384 00:20:20,351 --> 00:20:23,888 But I do want you to know about these two key factors, which 385 00:20:23,888 --> 00:20:25,990 are half filling and fully filling 386 00:20:25,990 --> 00:20:28,259 leading to enhanced stability. 387 00:20:28,259 --> 00:20:29,260 All right, good. 388 00:20:29,260 --> 00:20:31,462 OK, so we got valence. 389 00:20:31,462 --> 00:20:33,231 We got filling. 390 00:20:33,231 --> 00:20:39,170 Now, right away, right away, all right-- 391 00:20:39,170 --> 00:20:47,445 so by the way, configurations are in here. 392 00:20:47,445 --> 00:20:48,546 It's a beautiful thing. 393 00:20:48,546 --> 00:20:52,283 When I look at this, I now can look at this line in here 394 00:20:52,283 --> 00:20:53,985 that shows-- 395 00:20:53,985 --> 00:20:58,122 that shows using this notation, the filling 396 00:20:58,122 --> 00:21:01,659 of electrons for every single atom, every single atom. 397 00:21:01,659 --> 00:21:06,130 And it's a beautiful thing because it tells us so 398 00:21:06,130 --> 00:21:07,999 much about the periodic table. 399 00:21:07,999 --> 00:21:11,569 It tells us so much about why the periodic table is 400 00:21:11,569 --> 00:21:12,270 what it is. 401 00:21:12,270 --> 00:21:14,005 It was arranged. 402 00:21:14,005 --> 00:21:19,477 Right, it was arranged because of things like the combination, 403 00:21:19,477 --> 00:21:23,648 remember Mendeleev, mass and properties. 404 00:21:23,648 --> 00:21:25,850 But now we see why. 405 00:21:25,850 --> 00:21:27,151 We see why. 406 00:21:27,151 --> 00:21:30,588 It's incredible, because it goes back to counting. 407 00:21:30,588 --> 00:21:32,156 It literally goes back to the quantum 408 00:21:32,156 --> 00:21:35,159 mechanical derivations of orbitals 409 00:21:35,159 --> 00:21:36,694 and the principles of filling them, 410 00:21:36,694 --> 00:21:38,296 and then the filling them themselves. 411 00:21:38,296 --> 00:21:40,698 And you see, you know, why does the lanthanides 412 00:21:40,698 --> 00:21:45,169 and actinides, why did those things run for 14? 413 00:21:45,169 --> 00:21:46,537 Because that's how many electrons 414 00:21:46,537 --> 00:21:48,673 go into the f orbitals. 415 00:21:48,673 --> 00:21:52,343 Right, that's how many electrons go into 4f and 5f. 416 00:21:52,343 --> 00:21:53,911 That's why these are 14. 417 00:21:53,911 --> 00:21:57,715 Why are these two columns here? 418 00:21:57,715 --> 00:22:01,152 Why do those have similar properties as you go down? 419 00:22:01,152 --> 00:22:03,821 Right, I mentioned lithium and sodium, right. 420 00:22:03,821 --> 00:22:05,323 Well, because of what we just said. 421 00:22:05,323 --> 00:22:07,292 You're increasing the principle quantum number, 422 00:22:07,292 --> 00:22:09,460 but the valence chemistry is very similar. 423 00:22:09,460 --> 00:22:11,929 They're all s. 424 00:22:11,929 --> 00:22:13,898 And we even call them sometimes these 425 00:22:13,898 --> 00:22:18,102 blocks by the valence chemistry that's getting filled. 426 00:22:18,102 --> 00:22:22,006 Right, so those first two columns are the s block. 427 00:22:22,006 --> 00:22:23,541 Here over here, they're the p block. 428 00:22:23,541 --> 00:22:26,644 It's not that these don't have p electrons in them. 429 00:22:26,644 --> 00:22:28,446 It's that these are the electrons that 430 00:22:28,446 --> 00:22:32,950 are getting added in this part, in this region, whereas here, 431 00:22:32,950 --> 00:22:34,919 you've got d electrons. 432 00:22:34,919 --> 00:22:37,922 And now we know exactly why this is 10. 433 00:22:37,922 --> 00:22:40,858 I mean, we know even more than this, because aufbau says, 434 00:22:40,858 --> 00:22:43,828 why is this here and not here? 435 00:22:43,828 --> 00:22:46,497 Right, because of the ordering of the filling, 436 00:22:46,497 --> 00:22:48,032 of the energies of the filling. 437 00:22:48,032 --> 00:22:51,235 These three d's come after 4s. 438 00:22:51,235 --> 00:22:52,970 That's why they're here. 439 00:22:52,970 --> 00:22:55,106 Right, that's why they belong here. 440 00:22:55,106 --> 00:22:57,975 We now know so much more. 441 00:22:57,975 --> 00:23:01,045 We have so much more insight into the ordering 442 00:23:01,045 --> 00:23:04,582 of the periodic table, because of electron filling. 443 00:23:04,582 --> 00:23:07,352 And we'll be making those connections. 444 00:23:07,352 --> 00:23:09,120 We'll be making those connections a lot. 445 00:23:09,120 --> 00:23:12,523 Right, but I just wanted to kind of show you 446 00:23:12,523 --> 00:23:15,760 the power of seeing things in terms of filling. 447 00:23:15,760 --> 00:23:17,595 The one connection I'll tell you about today 448 00:23:17,595 --> 00:23:19,130 has to do with diameter. 449 00:23:19,130 --> 00:23:20,998 OK, so we'll be making connections 450 00:23:20,998 --> 00:23:23,701 all throughout the class between electron filling 451 00:23:23,701 --> 00:23:25,536 and properties. 452 00:23:25,536 --> 00:23:30,341 Right, but let's start with a simple one, how big is an atom? 453 00:23:30,341 --> 00:23:32,910 Well, now you can understand some things. 454 00:23:32,910 --> 00:23:36,814 Right, so for example, if I plot here or if Averill plots it, 455 00:23:36,814 --> 00:23:38,916 and I take that from Averill and show it 456 00:23:38,916 --> 00:23:41,252 to you, the probability-- 457 00:23:41,252 --> 00:23:44,622 remember we plotted this before for 1s, 2s. 458 00:23:44,622 --> 00:23:48,259 Now, what they plot here, OK, the 1s orbital 459 00:23:48,259 --> 00:23:50,995 for helium, that's got two electrons in it. 460 00:23:50,995 --> 00:23:53,197 There it is right there, the 1s, and then 461 00:23:53,197 --> 00:23:54,832 the 2s and 2p combined. 462 00:23:54,832 --> 00:23:56,934 Right, everything is sort of thrown together here. 463 00:23:56,934 --> 00:24:00,204 They're not separated for neon and then argon. 464 00:24:00,204 --> 00:24:04,108 So these are the first three noble gases, helium, neon, 465 00:24:04,108 --> 00:24:04,909 argon. 466 00:24:04,909 --> 00:24:06,310 OK. 467 00:24:06,310 --> 00:24:07,445 And a couple of things. 468 00:24:07,445 --> 00:24:13,551 One thing you can see is that the s electrons in helium 469 00:24:13,551 --> 00:24:15,686 are furthest out. 470 00:24:15,686 --> 00:24:18,856 And then the neon ones are closer in, and look at that. 471 00:24:18,856 --> 00:24:20,591 The argon ones are even closer. 472 00:24:20,591 --> 00:24:22,493 Why? 473 00:24:22,493 --> 00:24:27,598 Why are the 1s electrons getting closer in 474 00:24:27,598 --> 00:24:30,034 as I add more electrons? 475 00:24:30,034 --> 00:24:30,935 Right. 476 00:24:30,935 --> 00:24:33,838 Well, it has to do with what we talked about Monday. 477 00:24:33,838 --> 00:24:36,707 Those 1s electrons are not screened. 478 00:24:36,707 --> 00:24:39,844 So what they see as you go from helium to neon to argon 479 00:24:39,844 --> 00:24:43,614 is more and more positive charge. 480 00:24:43,614 --> 00:24:45,516 In fact, I've got the numbers here, 481 00:24:45,516 --> 00:24:49,153 if you look at the 1s electron energy, 482 00:24:49,153 --> 00:24:53,791 remember for hydrogen, 13.6. 483 00:24:53,791 --> 00:24:55,693 Now remember, I didn't write a value there. 484 00:24:55,693 --> 00:24:56,894 But there's two protons. 485 00:24:56,894 --> 00:25:00,231 So that 1s electron for helium. 486 00:25:00,231 --> 00:25:06,871 So if we take 1s electron energy, so much abbreviation. 487 00:25:06,871 --> 00:25:10,241 For helium, it's 24.5 eV. 488 00:25:10,241 --> 00:25:11,876 That's how much it would take. 489 00:25:11,876 --> 00:25:14,745 So we can put minus, if you want to compare with this, 490 00:25:14,745 --> 00:25:16,113 right, this minus 13.6. 491 00:25:16,113 --> 00:25:17,548 That's also how much it would take 492 00:25:17,548 --> 00:25:20,651 to ionize that 1s electron. 493 00:25:20,651 --> 00:25:22,086 That's where it sits. 494 00:25:22,086 --> 00:25:31,762 But if you look at neon, neon is minus 869.5 eV. 495 00:25:31,762 --> 00:25:37,401 And argon is minus 3,206 eV. 496 00:25:37,401 --> 00:25:38,903 That is a lot of energy. 497 00:25:38,903 --> 00:25:40,204 That is a lot more energy. 498 00:25:40,204 --> 00:25:42,206 That is much, much happier. 499 00:25:42,206 --> 00:25:44,842 If energy-- if lower energy is happiness, 500 00:25:44,842 --> 00:25:47,211 those 1s electrons are super happy, 501 00:25:47,211 --> 00:25:50,214 and they get closer to all that positive charge. 502 00:25:50,214 --> 00:25:55,319 But you can also understand why, like neon is larger 503 00:25:55,319 --> 00:25:59,323 than helium, and argon, even though these energies of the 1s 504 00:25:59,323 --> 00:26:01,526 are closer and closer, these are still 505 00:26:01,526 --> 00:26:07,298 going to be larger, because as you go down in a column, 506 00:26:07,298 --> 00:26:09,800 you add a whole shell. 507 00:26:09,800 --> 00:26:11,435 Right, so I can't-- 508 00:26:11,435 --> 00:26:13,604 right, so remember, here's my plus charge. 509 00:26:13,604 --> 00:26:15,606 Here's my minus charge. 510 00:26:15,606 --> 00:26:18,242 I can't-- this is 1s. 511 00:26:18,242 --> 00:26:20,611 Now I can't add anything in here. 512 00:26:20,611 --> 00:26:24,882 I got to add stuff out here and go out. 513 00:26:24,882 --> 00:26:29,620 Remember those principle quantum numbers, 1 to 2? 514 00:26:29,620 --> 00:26:32,890 Right, we don't need the s here, just 1 to 2 to 3, 515 00:26:32,890 --> 00:26:35,726 they're going to push you further and further out. 516 00:26:35,726 --> 00:26:37,094 We talked about that Monday. 517 00:26:37,094 --> 00:26:39,463 So now the next electrons that come 518 00:26:39,463 --> 00:26:43,467 in in neon's case in 2s or 2p or in argon's case, 3s and 3p, 519 00:26:43,467 --> 00:26:45,202 those are going to come much further out. 520 00:26:45,202 --> 00:26:48,806 That's why when you look at size, which is what's 521 00:26:48,806 --> 00:26:51,576 shown here, you see this trend. 522 00:26:51,576 --> 00:26:52,209 All right. 523 00:26:52,209 --> 00:26:55,813 So you see this trend that as you go down a column, here 524 00:26:55,813 --> 00:26:56,547 they are. 525 00:26:56,547 --> 00:26:57,114 Here they are. 526 00:26:57,114 --> 00:27:00,017 So this is the size in the periodic table, 527 00:27:00,017 --> 00:27:02,119 and these are calculated. 528 00:27:02,119 --> 00:27:03,020 These are calculated. 529 00:27:03,020 --> 00:27:04,021 Why are they calculated? 530 00:27:04,021 --> 00:27:07,124 Because you can see, this should be pretty hard to measure. 531 00:27:07,124 --> 00:27:10,294 Right, these are hard to measure unless the atoms are 532 00:27:10,294 --> 00:27:14,298 in like a solid, and they're bonded together. 533 00:27:14,298 --> 00:27:17,234 So measured atomic radii are often 534 00:27:17,234 --> 00:27:20,204 taking half of a bond length. 535 00:27:20,204 --> 00:27:22,873 But we can also calculate them. 536 00:27:22,873 --> 00:27:25,409 And that's why these are calculated atomic radii. 537 00:27:25,409 --> 00:27:26,644 So these have no bonding. 538 00:27:26,644 --> 00:27:29,013 They're just isolated, and they're calculated 539 00:27:29,013 --> 00:27:32,216 and there's helium, neon, and argon. 540 00:27:32,216 --> 00:27:32,950 OK, fine. 541 00:27:32,950 --> 00:27:34,518 So we just understood that. 542 00:27:34,518 --> 00:27:37,054 And we understood this arrow that the radii 543 00:27:37,054 --> 00:27:39,590 get larger as you go down the periodic table. 544 00:27:39,590 --> 00:27:41,892 But what about going across? 545 00:27:41,892 --> 00:27:43,260 Why? 546 00:27:43,260 --> 00:27:46,263 I'm adding stuff to the atom. 547 00:27:46,263 --> 00:27:49,266 I'm filling lithium here. 548 00:27:49,266 --> 00:27:56,240 I'm adding an electron and from lithium there to beryllium. 549 00:27:56,240 --> 00:27:58,175 How can it get smaller? 550 00:27:58,175 --> 00:27:59,176 Right. 551 00:27:59,176 --> 00:28:01,078 How can it get smaller? 552 00:28:01,078 --> 00:28:03,981 So that has to do-- 553 00:28:03,981 --> 00:28:04,715 what did I do? 554 00:28:09,453 --> 00:28:11,555 OK, I'm going over here. 555 00:28:11,555 --> 00:28:12,256 All right. 556 00:28:12,256 --> 00:28:15,092 So that has to do with the fact-- 557 00:28:15,092 --> 00:28:17,194 with the same things that we've been talking about. 558 00:28:17,194 --> 00:28:20,731 It has to do with the fact that as I go from lithium. 559 00:28:20,731 --> 00:28:21,932 So OK, let's do this. 560 00:28:21,932 --> 00:28:26,303 If I have hydrogen, and I go to lithium, 561 00:28:26,303 --> 00:28:28,305 you know that it's going to be larger 562 00:28:28,305 --> 00:28:31,642 for the reasons I just said. 563 00:28:31,642 --> 00:28:36,213 But if I go from lithium over to beryllium, it gets smaller. 564 00:28:39,650 --> 00:28:42,453 And the reason is because of exactly this. 565 00:28:42,453 --> 00:28:49,727 If I go from hydrogen to lithium, I add protons. 566 00:28:49,727 --> 00:28:52,396 But I shield those protons with electrons. 567 00:28:52,396 --> 00:28:57,468 OK, but if I am at lithium, let's see, lithium is here. 568 00:28:57,468 --> 00:29:00,504 So I've got one, two, three. 569 00:29:00,504 --> 00:29:02,707 And I've got an electron here. 570 00:29:02,707 --> 00:29:05,976 Right, I've got two electrons in the 1s orbital, 571 00:29:05,976 --> 00:29:10,848 and then I've got one electron in the 2s orbital. 572 00:29:10,848 --> 00:29:13,050 OK, so that's lithium. 573 00:29:13,050 --> 00:29:15,219 But now I go to beryllium. 574 00:29:15,219 --> 00:29:21,992 And if I'm beryllium, I've got four. 575 00:29:21,992 --> 00:29:26,530 OK, and so now I've got those 2s electrons here. 576 00:29:26,530 --> 00:29:30,634 But see-- I'm sorry, 1s. 577 00:29:30,634 --> 00:29:34,872 But in the 2s orbital, I can put a second electron. 578 00:29:34,872 --> 00:29:38,909 Right, and so what happens is those two electrons 579 00:29:38,909 --> 00:29:42,546 in the 2s orbital, they don't really screen each other. 580 00:29:42,546 --> 00:29:45,916 They are screened by the 1s orbital. 581 00:29:45,916 --> 00:29:47,251 So if I now-- 582 00:29:47,251 --> 00:29:51,822 because I went-- even though I added an electron, 583 00:29:51,822 --> 00:29:54,725 I also have a lot more charge here. 584 00:29:54,725 --> 00:29:57,762 Right, and because these two don't screen each other, 585 00:29:57,762 --> 00:30:02,199 but these two do, right, these are going to be closer in, 586 00:30:02,199 --> 00:30:03,534 because they're more attracted. 587 00:30:03,534 --> 00:30:07,571 They're only screened by these two electrons. 588 00:30:07,571 --> 00:30:10,941 So the additional positive charge wins. 589 00:30:10,941 --> 00:30:13,811 If I go down in quantum number, then I 590 00:30:13,811 --> 00:30:16,947 get a whole shelf filled to screen. 591 00:30:16,947 --> 00:30:19,216 But here, I'm just adding another electron 592 00:30:19,216 --> 00:30:22,019 to the same orbital to the 2s orbital. 593 00:30:22,019 --> 00:30:24,321 But I've got a hold other proton, and the shielding, 594 00:30:24,321 --> 00:30:26,857 the screening is the same. 595 00:30:26,857 --> 00:30:30,427 That's why beryllium is smaller than lithium, 596 00:30:30,427 --> 00:30:32,029 even though you've added an electron. 597 00:30:32,029 --> 00:30:35,399 And it's why the trend goes like this, increasing that way, 598 00:30:35,399 --> 00:30:37,434 decreasing that way. 599 00:30:37,434 --> 00:30:41,405 Now, I like dancing. 600 00:30:41,405 --> 00:30:44,141 And so I like this dancing analogy, 601 00:30:44,141 --> 00:30:47,778 because I love thinking about atoms as dancing. 602 00:30:47,778 --> 00:30:50,080 I told you about the disco and the periodic table. 603 00:30:50,080 --> 00:30:52,850 But you can take that all the way to the atom. 604 00:30:52,850 --> 00:30:56,453 So you know, you can imagine that you're an electron, 605 00:30:56,453 --> 00:30:58,889 and you see a proton. 606 00:30:58,889 --> 00:31:02,259 OK, so dance pairs are happy. 607 00:31:02,259 --> 00:31:06,430 Dancers are happy if they have more people to dance with. 608 00:31:06,430 --> 00:31:08,532 And so if I'm hydrogen, and I'm an electron, 609 00:31:08,532 --> 00:31:12,002 and I see a proton, protons can only dance with electrons. 610 00:31:12,002 --> 00:31:13,470 And then I say, OK, let's dance. 611 00:31:13,470 --> 00:31:15,639 And you kind of start moving, you know, a little bit. 612 00:31:15,639 --> 00:31:20,344 And but now, I'm going to go to helium. 613 00:31:20,344 --> 00:31:22,913 So there's another dancer in the middle, 614 00:31:22,913 --> 00:31:26,250 and someone comes on, and says, oh OK, that's cool, right. 615 00:31:26,250 --> 00:31:26,851 I can-- 616 00:31:26,851 --> 00:31:30,754 Now, either one of us can dance with either one of those. 617 00:31:30,754 --> 00:31:32,556 All right, so I've got two different people. 618 00:31:32,556 --> 00:31:35,659 I'm happier closer in. 619 00:31:35,659 --> 00:31:37,494 We can get close, because there's choices 620 00:31:37,494 --> 00:31:40,731 for who you can dance with. 621 00:31:40,731 --> 00:31:42,466 All right. 622 00:31:42,466 --> 00:31:48,405 So that's why you get helium much smaller than hydrogen. 623 00:31:48,405 --> 00:31:49,874 More people to dance with. 624 00:31:49,874 --> 00:31:51,876 Now you're lithium, and you come along, 625 00:31:51,876 --> 00:31:54,311 and I'm a lithium electron here, and I'm 626 00:31:54,311 --> 00:31:56,113 like I want to dance with somebody. 627 00:31:56,113 --> 00:31:57,014 Who's there? 628 00:31:57,014 --> 00:31:59,884 And there's only one person, because these two people 629 00:31:59,884 --> 00:32:01,652 are totally occupied. 630 00:32:01,652 --> 00:32:04,021 I only have one possibility for people 631 00:32:04,021 --> 00:32:08,425 to dance with if I'm this lithium electron. 632 00:32:08,425 --> 00:32:13,163 Right, but now I come in, and I'm beryllium, and these two 633 00:32:13,163 --> 00:32:14,531 electrons, and they're both like, 634 00:32:14,531 --> 00:32:17,234 well, OK, you guys are blocking, whatever. 635 00:32:17,234 --> 00:32:18,702 That's not cool. 636 00:32:18,702 --> 00:32:20,304 But there's four people in the middle. 637 00:32:20,304 --> 00:32:22,806 So there's always two or three people, right, 638 00:32:22,806 --> 00:32:24,041 that we can dance with. 639 00:32:24,041 --> 00:32:25,075 That wasn't like a move. 640 00:32:25,075 --> 00:32:26,510 I don't know what that was. 641 00:32:26,510 --> 00:32:29,713 But I'm like I can dance with you or I can dance with you. 642 00:32:29,713 --> 00:32:34,885 And more dancing choices, happier. 643 00:32:34,885 --> 00:32:38,822 Happier, lower energy. 644 00:32:38,822 --> 00:32:40,357 So that's how I like to see atoms. 645 00:32:43,160 --> 00:32:47,264 OK, so that's one example of filling and screening 646 00:32:47,264 --> 00:32:53,837 and dancing, where this kind of picture of the atoms, 647 00:32:53,837 --> 00:32:59,209 this electron filling of the orbitals explains what we see. 648 00:32:59,209 --> 00:33:02,947 OK, now, we talked about ionization, 649 00:33:02,947 --> 00:33:07,284 and we talked about how sometimes those outer electrons 650 00:33:07,284 --> 00:33:12,589 can be lost, or sometimes, maybe an atom would 651 00:33:12,589 --> 00:33:15,225 gain an outer electron. 652 00:33:15,225 --> 00:33:20,564 If an electron is lost from an atom, called an ion. 653 00:33:20,564 --> 00:33:35,045 And so a charged atom is an ion, and a cation 654 00:33:35,045 --> 00:33:40,517 is a positive charge, positive charge. 655 00:33:40,517 --> 00:33:42,419 Abbreviations. 656 00:33:42,419 --> 00:33:44,888 Right, and so here's sodium, and it's 657 00:33:44,888 --> 00:33:49,159 got all those dancers in there, and it has lost an electron. 658 00:33:49,159 --> 00:33:50,227 There it is. 659 00:33:50,227 --> 00:33:51,762 It's going to lose-- 660 00:33:51,762 --> 00:33:54,898 remember we talked about the first ionization potential. 661 00:33:54,898 --> 00:33:56,166 We talked about that last week. 662 00:33:56,166 --> 00:33:59,169 It's going to lose that lowest-- 663 00:33:59,169 --> 00:34:01,005 sorry, the highest energy electron, 664 00:34:01,005 --> 00:34:03,240 the least bound electron, the one that's 665 00:34:03,240 --> 00:34:05,442 all the way out there. 666 00:34:05,442 --> 00:34:07,611 And so if it does, it's NA plus. 667 00:34:07,611 --> 00:34:10,981 OK, gesundheit. 668 00:34:10,981 --> 00:34:12,282 Now, you can also-- 669 00:34:12,282 --> 00:34:13,183 this is from Averill. 670 00:34:13,183 --> 00:34:15,819 You can also lose more than that. 671 00:34:15,819 --> 00:34:18,722 All right, magnesium might lose two electrons. 672 00:34:18,722 --> 00:34:20,724 So the gray part here is the ion, 673 00:34:20,724 --> 00:34:24,094 and the blue part is the original neutral atom, 674 00:34:24,094 --> 00:34:25,262 all right. 675 00:34:25,262 --> 00:34:28,364 And you can see that if sodium loses one electron, 676 00:34:28,364 --> 00:34:30,199 and magnesium loses two, those actually 677 00:34:30,199 --> 00:34:32,101 have the same number of electrons. 678 00:34:32,101 --> 00:34:33,270 They're different atoms. 679 00:34:33,270 --> 00:34:36,572 Those are called isoelectronic. 680 00:34:36,572 --> 00:34:38,475 Well, you can also gain electrons. 681 00:34:38,475 --> 00:34:39,576 So if you write that down. 682 00:34:39,576 --> 00:34:42,312 So you know, if you gain electrons, 683 00:34:42,312 --> 00:34:44,815 does anybody know what those are called? 684 00:34:44,815 --> 00:34:52,389 Anion, OK, negative charge would be in an anion. 685 00:34:52,389 --> 00:34:55,958 OK, and I can ask question. 686 00:34:55,958 --> 00:34:58,862 If I lose an electron, it makes sense that I got smaller. 687 00:34:58,862 --> 00:35:00,130 This is the radius. 688 00:35:00,130 --> 00:35:02,099 And if I gain, it make sense that I got bigger. 689 00:35:02,099 --> 00:35:04,034 And I can mix it up. 690 00:35:04,034 --> 00:35:09,239 So I could ask you a question, like what's the ordering-- 691 00:35:09,239 --> 00:35:13,343 what's the ordering of these atoms. 692 00:35:13,343 --> 00:35:20,784 Right, I could say, well, if I had Mg 2 plus and Ca 2 plus, 693 00:35:20,784 --> 00:35:25,522 and Ca, what's the ordering of their size? 694 00:35:25,522 --> 00:35:27,991 You now know how to answer questions like this, right? 695 00:35:27,991 --> 00:35:30,260 If I lose electrons, I'm going to get smaller. 696 00:35:30,260 --> 00:35:32,129 If I gain electrons, I'm going to get bigger. 697 00:35:32,129 --> 00:35:38,435 But I also know that for example, Ca 2 plus 698 00:35:38,435 --> 00:35:44,541 is smaller than Ca, and Ca is bigger than Mg. 699 00:35:44,541 --> 00:35:45,008 Right. 700 00:35:45,008 --> 00:35:50,547 And so Ca 2 plus is going to be bigger than Mg 2 plus. 701 00:35:50,547 --> 00:35:52,816 Right, that makes a lot of sense. 702 00:35:52,816 --> 00:35:53,750 Done. 703 00:35:53,750 --> 00:35:54,918 You can order them now. 704 00:35:54,918 --> 00:35:58,355 All right, so Ca must be bigger than Ca 2 plus, 705 00:35:58,355 --> 00:36:00,023 and that must be bigger than Mg 2 plus. 706 00:36:00,023 --> 00:36:03,293 So we can think about now adding in ions to the mix. 707 00:36:03,293 --> 00:36:05,195 And we're doing this for a reason. 708 00:36:05,195 --> 00:36:08,899 All right, we're doing this for a reason. 709 00:36:08,899 --> 00:36:16,206 But because, you see, some atoms really don't mind doing this. 710 00:36:16,206 --> 00:36:16,940 They really don't. 711 00:36:16,940 --> 00:36:18,575 Sodium is one of them. 712 00:36:18,575 --> 00:36:19,776 They don't mind losing atoms. 713 00:36:19,776 --> 00:36:21,478 I mean, yeah, the electron is there. 714 00:36:21,478 --> 00:36:25,315 But it's kind of there as sort of like, I could be here, 715 00:36:25,315 --> 00:36:26,416 I can be there. 716 00:36:26,416 --> 00:36:27,317 I'm good. 717 00:36:27,317 --> 00:36:29,486 Whereas those 1s electrons, you know 718 00:36:29,486 --> 00:36:31,421 the 1s electrons are argon, are like you just 719 00:36:31,421 --> 00:36:33,223 try to take me out. 720 00:36:33,223 --> 00:36:36,193 All right, no way. 721 00:36:36,193 --> 00:36:37,661 But we will. 722 00:36:37,661 --> 00:36:41,431 We will ionize those next week. 723 00:36:41,431 --> 00:36:43,700 But for now, we're taking these outer ones out 724 00:36:43,700 --> 00:36:46,303 that may not be strongly balanced. 725 00:36:46,303 --> 00:36:48,939 They're happy, losing or gaining. 726 00:36:48,939 --> 00:36:50,307 And how do you know? 727 00:36:50,307 --> 00:36:51,208 How do you know? 728 00:36:51,208 --> 00:36:55,812 If you have ions, how do you know, you know, 729 00:36:55,812 --> 00:36:56,713 whether you have them? 730 00:36:56,713 --> 00:37:00,083 Well, here's the deal, you now know 731 00:37:00,083 --> 00:37:02,886 a way to tell because in this goodie bag, which I'll 732 00:37:02,886 --> 00:37:04,788 talk about in a few minutes, you actually 733 00:37:04,788 --> 00:37:09,726 have the most accurate measuring device ever made. 734 00:37:09,726 --> 00:37:10,961 You have a scale. 735 00:37:10,961 --> 00:37:12,829 That's not-- no. 736 00:37:12,829 --> 00:37:14,464 It's in here somewhere. 737 00:37:14,464 --> 00:37:18,835 You have a conductivity meter, somewhere in here, 738 00:37:18,835 --> 00:37:21,271 which I cannot find. 739 00:37:21,271 --> 00:37:23,807 And the conductivity meter is exactly that. 740 00:37:23,807 --> 00:37:24,641 There it is. 741 00:37:24,641 --> 00:37:28,245 Oh, look at this. 742 00:37:28,245 --> 00:37:29,179 This is incredible. 743 00:37:29,179 --> 00:37:31,915 So you can put this into a solution, 744 00:37:31,915 --> 00:37:33,650 and it literally just measures-- it's 745 00:37:33,650 --> 00:37:35,485 got two electrodes that go in there, 746 00:37:35,485 --> 00:37:37,554 and it measures whether there's any conduction, 747 00:37:37,554 --> 00:37:39,990 and you can see, well, if I've got charge 748 00:37:39,990 --> 00:37:44,461 species in the solution, ions, then this will tell you, 749 00:37:44,461 --> 00:37:47,130 because they'll help conduct electricity. 750 00:37:47,130 --> 00:37:52,569 So you now have a way of knowing when you have ions or not. 751 00:37:52,569 --> 00:37:55,405 OK, so that's good. 752 00:37:55,405 --> 00:37:58,375 But you see, the thing is something very important 753 00:37:58,375 --> 00:38:01,878 happens when atoms come together-- 754 00:38:01,878 --> 00:38:04,514 when atoms-- don't measure anything yet. 755 00:38:04,514 --> 00:38:05,782 But take it to lunch. 756 00:38:05,782 --> 00:38:07,784 Take it to lunch. 757 00:38:07,784 --> 00:38:09,319 You don't know. 758 00:38:09,319 --> 00:38:10,787 People talk about electrolytes. 759 00:38:10,787 --> 00:38:12,689 They talk a big game. 760 00:38:12,689 --> 00:38:13,156 All right. 761 00:38:13,156 --> 00:38:21,231 Now, the thing is when atoms react, when-- 762 00:38:21,231 --> 00:38:25,402 this sounds like the beginning of a novel. 763 00:38:25,402 --> 00:38:32,709 When atoms react, right, sometimes they 764 00:38:32,709 --> 00:38:34,911 will gain or lose. 765 00:38:34,911 --> 00:38:40,717 When atoms react, they may want to gain or lose 766 00:38:40,717 --> 00:38:51,328 the amount of electrons to get them to the closest noble gas. 767 00:38:51,328 --> 00:38:56,099 OK, closest noble gas. 768 00:38:56,099 --> 00:38:57,901 Now, that's really important. 769 00:38:57,901 --> 00:38:59,936 We just talked about how you use the noble gas 770 00:38:59,936 --> 00:39:01,705 notation-- did I just erase it? 771 00:39:01,705 --> 00:39:04,574 I did. 772 00:39:04,574 --> 00:39:07,477 Because that could be chemically inert. 773 00:39:07,477 --> 00:39:09,846 And we can only go down when we do the notation, 774 00:39:09,846 --> 00:39:12,115 but now we can go up, because I could add electrons 775 00:39:12,115 --> 00:39:15,118 to get to the nearest noble gas, in terms of reacting. 776 00:39:15,118 --> 00:39:16,653 And look at this. 777 00:39:16,653 --> 00:39:20,023 If sodium is an atom that doesn't mind losing electrons 778 00:39:20,023 --> 00:39:23,760 and chlorine is an atom that really wants to gain electrons, 779 00:39:23,760 --> 00:39:27,864 and they come together, and they come together, 780 00:39:27,864 --> 00:39:30,367 then you can form a bond. 781 00:39:30,367 --> 00:39:33,403 Oh, oh boy. 782 00:39:33,403 --> 00:39:35,672 Here we are I guaranteed you. 783 00:39:35,672 --> 00:39:38,308 I told you on Monday, we would get here. 784 00:39:38,308 --> 00:39:40,777 I said, it's our three week anniversary, 785 00:39:40,777 --> 00:39:44,114 and I think we're going to bond. 786 00:39:44,114 --> 00:39:49,219 First bond, first bond. 787 00:39:49,219 --> 00:39:51,154 And it's ionic. 788 00:39:51,154 --> 00:39:51,788 It's ionic. 789 00:39:55,992 --> 00:40:08,405 Because this is a bond of an electrostatic attraction. 790 00:40:08,405 --> 00:40:11,541 This is the bond of electrostatic attraction 791 00:40:11,541 --> 00:40:16,980 between two oppositely charged atoms. 792 00:40:16,980 --> 00:40:30,160 So between two oppositely charged atoms. 793 00:40:30,160 --> 00:40:32,996 And so if I've got a positive and a negative, 794 00:40:32,996 --> 00:40:34,197 they're going to be attracted. 795 00:40:34,197 --> 00:40:35,665 How are they going to be attracted? 796 00:40:35,665 --> 00:40:38,268 Well, actually that's an attraction 797 00:40:38,268 --> 00:40:39,669 that we know all about. 798 00:40:39,669 --> 00:40:40,303 Oh there it is. 799 00:40:40,303 --> 00:40:40,804 Hold up. 800 00:40:40,804 --> 00:40:42,205 We just made our first bond. 801 00:40:42,205 --> 00:40:43,440 Let's talk about it. 802 00:40:43,440 --> 00:40:44,841 What do I want to say? 803 00:40:44,841 --> 00:40:46,476 I want to talk about that attraction. 804 00:40:46,476 --> 00:40:47,944 Because that's actually attraction 805 00:40:47,944 --> 00:40:48,912 that we know very well. 806 00:40:48,912 --> 00:40:50,547 It's a Coulomb attraction. 807 00:40:50,547 --> 00:40:53,316 Right, and so the way this works is 808 00:40:53,316 --> 00:40:56,052 if I'm an atom with positive charge, 809 00:40:56,052 --> 00:40:58,588 and I'm an atom with negative charge. 810 00:40:58,588 --> 00:41:01,024 All right, so let's take that same example, 811 00:41:01,024 --> 00:41:02,025 and this is the energy. 812 00:41:05,695 --> 00:41:08,131 And this is say, zero. 813 00:41:08,131 --> 00:41:11,935 And this is the distance between the two atoms. 814 00:41:11,935 --> 00:41:15,338 If I'm out here, then maybe the distance 815 00:41:15,338 --> 00:41:20,477 between sodium and chlorine is very far. 816 00:41:20,477 --> 00:41:22,512 But you see there's a Coulomb attraction. 817 00:41:22,512 --> 00:41:27,451 And so the attraction is Coulomb, 818 00:41:27,451 --> 00:41:29,853 which is going to be minus a constant times 819 00:41:29,853 --> 00:41:37,060 the charges on those ions over the distance between them. 820 00:41:37,060 --> 00:41:38,728 All right. 821 00:41:38,728 --> 00:41:40,797 So that-- if I draw that attraction, 822 00:41:40,797 --> 00:41:50,907 this is the charges on ions, charges on ions. 823 00:41:50,907 --> 00:41:54,277 And if I draw that, the Coulomb attraction looks like this. 824 00:41:54,277 --> 00:41:55,011 That's it. 825 00:41:55,011 --> 00:41:57,113 Right, that's 1 over r. 826 00:41:57,113 --> 00:41:59,449 But see, the thing is if they get too close, 827 00:41:59,449 --> 00:42:03,453 then those core, you know, then things start to repel. 828 00:42:03,453 --> 00:42:05,021 It's like, whoa, whoa. 829 00:42:05,021 --> 00:42:05,822 Hold on. 830 00:42:05,822 --> 00:42:08,658 I'm not going to go any further, because I 831 00:42:08,658 --> 00:42:13,630 don't like having the same charges getting too close, 832 00:42:13,630 --> 00:42:14,531 right. 833 00:42:14,531 --> 00:42:15,298 I don't like that. 834 00:42:15,298 --> 00:42:17,667 Your electrons are getting too close to my electrons, 835 00:42:17,667 --> 00:42:20,837 and don't make me go nuclear. 836 00:42:20,837 --> 00:42:24,307 And so what you get is you get something like this. 837 00:42:27,544 --> 00:42:32,516 And this would be the potential energy of those two ions. 838 00:42:32,516 --> 00:42:34,584 They can't get super duper close. 839 00:42:34,584 --> 00:42:37,020 But when they're far away, they're kind of free, and then 840 00:42:37,020 --> 00:42:38,388 as they get a little closer, they 841 00:42:38,388 --> 00:42:40,924 start feeling that attraction, that Coulomb attraction. 842 00:42:40,924 --> 00:42:47,430 And this energy here, this energy has a name. 843 00:42:47,430 --> 00:42:57,040 It's called the lattice energy, because for the solid, right? 844 00:42:57,040 --> 00:43:03,547 So if I make a solid out of these types of ions, 845 00:43:03,547 --> 00:43:06,049 and now I break it all up, and I go all the way out 846 00:43:06,049 --> 00:43:09,619 to just loan ion, so I go from the isolated 847 00:43:09,619 --> 00:43:15,825 ions to a solid of these ionic bonds, then I gain this energy. 848 00:43:15,825 --> 00:43:18,695 And it takes that energy to break them back up. 849 00:43:18,695 --> 00:43:20,063 That's called the lattice energy. 850 00:43:20,063 --> 00:43:21,431 And you can see right away, there 851 00:43:21,431 --> 00:43:24,734 are some really kind of interesting observations 852 00:43:24,734 --> 00:43:28,004 you can make related to this simple relationship 853 00:43:28,004 --> 00:43:31,374 of a Coulomb attraction for an ionic bond. 854 00:43:31,374 --> 00:43:34,344 All right, so here's two ionic solids. 855 00:43:34,344 --> 00:43:35,579 There's sodium chloride. 856 00:43:35,579 --> 00:43:36,546 There's magnesium oxide. 857 00:43:36,546 --> 00:43:39,916 There's Na plus and F minus. 858 00:43:39,916 --> 00:43:42,919 OK, and notice the Coulomb energy here. 859 00:43:42,919 --> 00:43:44,921 And notice the differences in the lattice energy. 860 00:43:44,921 --> 00:43:47,924 This is like four times that. 861 00:43:47,924 --> 00:43:52,862 That is exactly what you get from this, because in this case 862 00:43:52,862 --> 00:43:55,932 Q1 and Q2 are both 1, right, 1 and negative 1. 863 00:43:55,932 --> 00:44:00,637 And here, Q1 and Q2 are both 2, and negative 2. 864 00:44:00,637 --> 00:44:03,740 So it should be four times, and that's, in fact, you 865 00:44:03,740 --> 00:44:06,409 can measure how much energy does it take to break this thing up, 866 00:44:06,409 --> 00:44:07,377 four times as much. 867 00:44:07,377 --> 00:44:08,878 That's the lattice energy. 868 00:44:08,878 --> 00:44:10,246 So we know something about this. 869 00:44:10,246 --> 00:44:12,515 And you can see trends. 870 00:44:12,515 --> 00:44:14,217 Right, so these are now the radii. 871 00:44:14,217 --> 00:44:16,953 We just talked about these. 872 00:44:16,953 --> 00:44:20,123 Right, radii for ions. 873 00:44:20,123 --> 00:44:22,058 And this is the lattice energy. 874 00:44:22,058 --> 00:44:25,428 And you can see that if I'm the smallest one, and the smallest 875 00:44:25,428 --> 00:44:27,330 one there, I have the highest lattice energy. 876 00:44:27,330 --> 00:44:29,332 And that's the 1 over r part. 877 00:44:29,332 --> 00:44:32,902 So you got the charge and how close they can get. 878 00:44:32,902 --> 00:44:35,605 And you now know from-- just from the trends we've just 879 00:44:35,605 --> 00:44:39,175 talked about, the radii trends we just talked about, 880 00:44:39,175 --> 00:44:43,713 you know how you might compare how much one ionic solid 881 00:44:43,713 --> 00:44:46,783 is bonded, compared to another, because you 882 00:44:46,783 --> 00:44:50,186 can talk about how much charge it might lose or gain. 883 00:44:50,186 --> 00:44:54,824 It likes to get close to the nearest noble gas. 884 00:44:54,824 --> 00:44:57,560 And you can also think about their size or relative sizes. 885 00:44:57,560 --> 00:44:59,696 So like the largest one with the largest 886 00:44:59,696 --> 00:45:05,001 has a larger r, and so weaker lattice energy. 887 00:45:05,001 --> 00:45:07,070 And boy, is this important. 888 00:45:07,070 --> 00:45:09,839 It changes all sorts of things about the properties 889 00:45:09,839 --> 00:45:15,578 of these solids, and that's why, we developed the goodie bag 890 00:45:15,578 --> 00:45:17,547 to help you explore that. 891 00:45:17,547 --> 00:45:19,215 So you have different solids. 892 00:45:19,215 --> 00:45:21,584 They're not all ionic, because you're 893 00:45:21,584 --> 00:45:23,720 talking about another kind of solid next week. 894 00:45:23,720 --> 00:45:25,388 Right, but you've got some ionic solids. 895 00:45:25,388 --> 00:45:27,857 And look, like, you know, so a lot of them 896 00:45:27,857 --> 00:45:31,127 dissolve, but if the lattice energy is so high, 897 00:45:31,127 --> 00:45:32,228 maybe it doesn't dissolve. 898 00:45:32,228 --> 00:45:34,197 Or maybe it's harder to dissolve. 899 00:45:34,197 --> 00:45:34,931 How do you know? 900 00:45:34,931 --> 00:45:37,300 Well, you could see it if you stir it. 901 00:45:37,300 --> 00:45:38,668 All right. 902 00:45:38,668 --> 00:45:40,303 But you also may be able to measure. 903 00:45:40,303 --> 00:45:42,338 Are there ions in solution? 904 00:45:42,338 --> 00:45:44,240 If there are ions in solution, than it 905 00:45:44,240 --> 00:45:49,045 could be a dissolved ionic solid that you've made. 906 00:45:49,045 --> 00:45:51,314 And so-- oh hardness, Mohs' scale. 907 00:45:51,314 --> 00:45:52,315 You can look that up. 908 00:45:52,315 --> 00:45:55,051 Did something scratch something else? 909 00:45:55,051 --> 00:45:55,752 Right. 910 00:45:55,752 --> 00:45:57,153 That's what that's related to. 911 00:45:57,153 --> 00:45:58,788 Melting point, right, the properties 912 00:45:58,788 --> 00:46:03,860 depend on this ionic bond. 913 00:46:03,860 --> 00:46:06,262 OK so there's the goodie bag, and then I'll 914 00:46:06,262 --> 00:46:08,531 do my why this matters in the last couple of minutes 915 00:46:08,531 --> 00:46:09,065 of class. 916 00:46:09,065 --> 00:46:10,600 All right, so there's the goodie bag. 917 00:46:10,600 --> 00:46:12,268 Oh, you've got a conductivity meter. 918 00:46:12,268 --> 00:46:14,504 You've got a scale. 919 00:46:14,504 --> 00:46:15,271 You've got a scale. 920 00:46:18,174 --> 00:46:20,376 I used to give that scale out with white powder right 921 00:46:20,376 --> 00:46:22,912 before Thanksgiving for a different goodie bag, 922 00:46:22,912 --> 00:46:25,081 and it was a really bad idea. 923 00:46:25,081 --> 00:46:28,918 But now it was-- 924 00:46:28,918 --> 00:46:31,921 it was citric acid, lime juice. 925 00:46:31,921 --> 00:46:34,824 But people traveled like that. 926 00:46:34,824 --> 00:46:36,025 And so we've learned. 927 00:46:36,025 --> 00:46:37,160 We've learned. 928 00:46:37,160 --> 00:46:39,529 And so we give it to you now, but please keep it. 929 00:46:39,529 --> 00:46:41,197 It's the world's most accurate scale. 930 00:46:41,197 --> 00:46:42,265 Why does this matter? 931 00:46:42,265 --> 00:46:45,368 Because look-- you're going to need the scale again. 932 00:46:45,368 --> 00:46:47,737 So please keep it. 933 00:46:47,737 --> 00:46:48,304 Here you go. 934 00:46:48,304 --> 00:46:50,573 Here's another chart of ionic bonds. 935 00:46:50,573 --> 00:46:52,809 These are lattice energies. 936 00:46:52,809 --> 00:46:56,412 OK, these are lattice energies, oh kilojoules per mole, 937 00:46:56,412 --> 00:46:57,680 it's just per mole of stuff. 938 00:46:57,680 --> 00:46:59,215 Right, don't get confused by that. 939 00:46:59,215 --> 00:47:02,285 Joules, electron volts, energies, per mole 940 00:47:02,285 --> 00:47:04,921 is per mole of atoms, right? 941 00:47:04,921 --> 00:47:08,792 OK, so we can isolate it down to one bond or a mole of bonds. 942 00:47:08,792 --> 00:47:12,929 All right, 15,000 for aluminum. 943 00:47:12,929 --> 00:47:13,563 Look at that. 944 00:47:13,563 --> 00:47:16,399 That's why aluminum is in your toothpaste. 945 00:47:16,399 --> 00:47:17,934 Aluminum oxide is in your toothpaste. 946 00:47:17,934 --> 00:47:19,702 It's in your pans. 947 00:47:19,702 --> 00:47:21,304 It's in sandpaper. 948 00:47:21,304 --> 00:47:23,706 It is a very hard material. 949 00:47:23,706 --> 00:47:24,974 It is a very hard material. 950 00:47:24,974 --> 00:47:25,608 Why? 951 00:47:25,608 --> 00:47:26,810 Because of this. 952 00:47:26,810 --> 00:47:27,811 Literally. 953 00:47:27,811 --> 00:47:31,447 Those Q's are really high, right? 954 00:47:31,447 --> 00:47:32,715 Why does this matter? 955 00:47:32,715 --> 00:47:36,052 Well, I'm going to give you an example in hemodialysis. 956 00:47:36,052 --> 00:47:37,887 Hemodialysis is something that people 957 00:47:37,887 --> 00:47:39,255 have to go into a hospital. 958 00:47:39,255 --> 00:47:44,694 People in their kidneys, don't clean their blood efficiently 959 00:47:44,694 --> 00:47:47,964 or enough have to have it cleaned by a machine, 960 00:47:47,964 --> 00:47:50,733 and 650,000 patients suffer from this 961 00:47:50,733 --> 00:47:53,469 and go to a hospital for literally four 962 00:47:53,469 --> 00:47:56,005 hours, three times a week. 963 00:47:56,005 --> 00:47:59,542 It devastates their weekly schedule. 964 00:47:59,542 --> 00:48:02,111 And if you could make this portable, 965 00:48:02,111 --> 00:48:05,348 you would change lives in a really big way. 966 00:48:05,348 --> 00:48:06,616 One of the big-- 967 00:48:06,616 --> 00:48:09,118 there are people out there trying to do this. 968 00:48:09,118 --> 00:48:12,822 This is an example of a design for a portable hemodialysis 969 00:48:12,822 --> 00:48:13,456 machine. 970 00:48:13,456 --> 00:48:17,260 One of the single biggest drawbacks in making it portable 971 00:48:17,260 --> 00:48:20,296 is making a filter, because you're filtering blood. 972 00:48:20,296 --> 00:48:22,732 You're filtering toxins out of the blood. 973 00:48:22,732 --> 00:48:24,567 It's something that the body can't do. 974 00:48:24,567 --> 00:48:27,670 So you need to do it for them. 975 00:48:27,670 --> 00:48:30,406 But the filters get mucked up and gunked up, 976 00:48:30,406 --> 00:48:32,775 and they're not strong enough, and they can't be cleaned. 977 00:48:32,775 --> 00:48:34,110 And look at this one. 978 00:48:34,110 --> 00:48:36,679 Here is a filter made out of aluminum. 979 00:48:36,679 --> 00:48:40,316 All right, and these things are what's needed. 980 00:48:40,316 --> 00:48:44,220 We need super strong, super resilient new filters 981 00:48:44,220 --> 00:48:45,922 that can filter things like blood 982 00:48:45,922 --> 00:48:47,523 and toxins out of the blood. 983 00:48:47,523 --> 00:48:49,926 So very, very tiny sizes that we can make over 984 00:48:49,926 --> 00:48:51,961 large areas and uniformly. 985 00:48:51,961 --> 00:48:53,663 This is the kind of starting material 986 00:48:53,663 --> 00:48:55,698 that we need to make new filters, 987 00:48:55,698 --> 00:48:56,866 and it all comes back down. 988 00:48:56,866 --> 00:48:58,601 Why would that be a good one if we 989 00:48:58,601 --> 00:49:00,169 can overcome it's brittleness? 990 00:49:00,169 --> 00:49:02,071 Because of the Q's. 991 00:49:02,071 --> 00:49:04,774 Because of the atom sizes, because of everything 992 00:49:04,774 --> 00:49:06,242 that we talked about today. 993 00:49:06,242 --> 00:49:10,713 So have a great long weekend, and see you guys next week.