1 00:00:00,090 --> 00:00:02,430 The following content is provided under a Creative 2 00:00:02,430 --> 00:00:03,820 Commons license. 3 00:00:03,820 --> 00:00:06,030 Your support will help MIT OpenCourseWare 4 00:00:06,030 --> 00:00:10,150 continue to offer high quality educational resources for free. 5 00:00:10,150 --> 00:00:12,690 To make a donation, or to view additional materials 6 00:00:12,690 --> 00:00:16,445 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:16,445 --> 00:00:17,070 at ocw.mit.edu. 8 00:00:26,260 --> 00:00:28,660 PROFESSOR: So, moving to today's handout, 9 00:00:28,660 --> 00:00:32,150 we're going to talk about crystal field theory. 10 00:00:32,150 --> 00:00:34,570 And we're going to talk about how 11 00:00:34,570 --> 00:00:37,390 the shapes of those orbitals can explain 12 00:00:37,390 --> 00:00:40,180 the special properties of transition metals, 13 00:00:40,180 --> 00:00:42,790 like color and magnetism. 14 00:00:42,790 --> 00:00:45,250 And really, as I said, the transition metals 15 00:00:45,250 --> 00:00:48,460 have amazing properties that can be absolutely gorgeous. 16 00:00:48,460 --> 00:00:50,500 They can do incredible things. 17 00:00:50,500 --> 00:00:52,480 They're very, very useful elements. 18 00:00:52,480 --> 00:00:54,910 I like to think of them as the super heroes 19 00:00:54,910 --> 00:00:56,650 of the periodic table. 20 00:00:56,650 --> 00:01:00,560 They're doing all the really spectacular stuff. 21 00:01:00,560 --> 00:01:02,740 So, today, we're going to talk about colors. 22 00:01:02,740 --> 00:01:05,560 And we're going to talk about whether things are magnetic, 23 00:01:05,560 --> 00:01:08,200 if they're paramagnetic, or diamagnetic. 24 00:01:08,200 --> 00:01:10,180 So, transition metals. 25 00:01:10,180 --> 00:01:13,840 I talked before about how they're useful in biology. 26 00:01:13,840 --> 00:01:18,480 They're also useful in terms of their beautiful colors. 27 00:01:18,480 --> 00:01:22,240 So, in the old days before you generated floor plans 28 00:01:22,240 --> 00:01:24,850 and drawings for buildings, on a computer 29 00:01:24,850 --> 00:01:27,130 you did blueprints for something. 30 00:01:27,130 --> 00:01:31,360 And the blue in the blueprint is actually a transition metal 31 00:01:31,360 --> 00:01:33,010 complex. 32 00:01:33,010 --> 00:01:37,150 And also, currently, it's an active area of research 33 00:01:37,150 --> 00:01:42,160 to design new imaging agents to use in MRIs, or to image 34 00:01:42,160 --> 00:01:43,780 the heart, or other things. 35 00:01:43,780 --> 00:01:47,170 And a lot of these also involve transition metal complexes. 36 00:01:47,170 --> 00:01:49,960 And the reason why they're useful, say, in an MRI 37 00:01:49,960 --> 00:01:52,510 is because they can have magnetic properties. 38 00:01:52,510 --> 00:01:55,340 So, scientists see these beautiful colors. 39 00:01:55,340 --> 00:01:57,700 It's kind of obvious that the transition metals often 40 00:01:57,700 --> 00:01:59,680 have these incredible colors. 41 00:01:59,680 --> 00:02:02,620 And they can put the transition metals in something 42 00:02:02,620 --> 00:02:05,792 with a magnet and see that they have magnetic properties. 43 00:02:05,792 --> 00:02:07,000 So these things were obvious. 44 00:02:07,000 --> 00:02:09,789 And then chemists want to try to understand why it's true. 45 00:02:09,789 --> 00:02:12,400 Why this particular metal behaves this way, or this metal 46 00:02:12,400 --> 00:02:14,110 has this particular color. 47 00:02:14,110 --> 00:02:16,390 And they like to try to categorize them and come up 48 00:02:16,390 --> 00:02:19,780 with theories that help to explain what 49 00:02:19,780 --> 00:02:21,580 they're observing in nature. 50 00:02:21,580 --> 00:02:23,740 And so, today, we're going to talk about one 51 00:02:23,740 --> 00:02:26,380 of those theories, which is Ligand field theory. 52 00:02:26,380 --> 00:02:28,660 And I'm also going to differentiate that-- or Crystal 53 00:02:28,660 --> 00:02:31,970 field theory and differentiate it from Ligand field theory. 54 00:02:31,970 --> 00:02:33,880 So both of these theories, again, 55 00:02:33,880 --> 00:02:38,140 are an attempt to explain the properties that we observe. 56 00:02:38,140 --> 00:02:40,970 And the idea behind it is pretty simple. 57 00:02:40,970 --> 00:02:44,470 You have a metal ion and a set of ligands around it. 58 00:02:44,470 --> 00:02:49,390 And if you compare the energy levels of that free metal ion-- 59 00:02:49,390 --> 00:02:52,270 so here's a free metal ion-- with that metal 60 00:02:52,270 --> 00:02:54,380 ion in a coordination complex-- here 61 00:02:54,380 --> 00:02:57,220 is quite a pretty coordination complex-- 62 00:02:57,220 --> 00:03:00,100 the energy levels are different. 63 00:03:00,100 --> 00:03:02,920 That's really all these theories are getting at. 64 00:03:02,920 --> 00:03:05,260 That there's a change when you bring ligands 65 00:03:05,260 --> 00:03:08,710 in around a transition metal. 66 00:03:08,710 --> 00:03:11,650 It changes the energy levels of those d orbitals. 67 00:03:11,650 --> 00:03:14,350 And if we understand how those de-energy levels change, 68 00:03:14,350 --> 00:03:16,600 we can understand a lot about the properties 69 00:03:16,600 --> 00:03:21,760 of that particular metal in that coordination environment. 70 00:03:21,760 --> 00:03:25,750 So energy levels are altered. 71 00:03:25,750 --> 00:03:28,750 So there's these two theories: Crystal field theory 72 00:03:28,750 --> 00:03:30,910 and Ligand field theory. 73 00:03:30,910 --> 00:03:34,840 Crystal field theory is the more simple one. 74 00:03:34,840 --> 00:03:40,170 It just considers the ionic description of the metal ligand 75 00:03:40,170 --> 00:03:41,230 bond. 76 00:03:41,230 --> 00:03:44,067 And so we talked about ionic bonds. 77 00:03:44,067 --> 00:03:46,150 And mostly you're just kind of thinking about them 78 00:03:46,150 --> 00:03:48,104 as these point charges. 79 00:03:48,104 --> 00:03:49,520 And you have plus, you have minus, 80 00:03:49,520 --> 00:03:51,820 and they attract each other. 81 00:03:51,820 --> 00:03:54,627 Covalent bonding is a bit more complicated. 82 00:03:54,627 --> 00:03:56,710 Start talking about hybridization and other things 83 00:03:56,710 --> 00:03:57,670 like that. 84 00:03:57,670 --> 00:03:59,630 So Crystal field theory is really simple. 85 00:03:59,630 --> 00:04:02,200 It just considers the ionic nature. 86 00:04:02,200 --> 00:04:03,730 And it does pretty well. 87 00:04:03,730 --> 00:04:06,230 It can explain a lot, but not everything. 88 00:04:06,230 --> 00:04:09,790 Ligand field theory has the covalent and the ionic, 89 00:04:09,790 --> 00:04:11,350 so it's a more complete description 90 00:04:11,350 --> 00:04:13,030 of that metal ligand bond. 91 00:04:13,030 --> 00:04:15,670 But this is more of an advanced topic. 92 00:04:15,670 --> 00:04:17,570 I just want you to know that that exists. 93 00:04:17,570 --> 00:04:20,680 So if you take 503 here in organic chemistry, 94 00:04:20,680 --> 00:04:22,660 we'll talk more about Ligand field theory. 95 00:04:22,660 --> 00:04:25,570 In this class we're just going to do Crystal field theory. 96 00:04:25,570 --> 00:04:27,880 But I like Crystal field theory because I like it 97 00:04:27,880 --> 00:04:30,310 when something that's pretty simple theory 98 00:04:30,310 --> 00:04:31,720 can explain a lot. 99 00:04:31,720 --> 00:04:34,540 I think a lot of nature can be explained by this. 100 00:04:34,540 --> 00:04:36,640 So if you really want to understand 101 00:04:36,640 --> 00:04:39,610 particular properties of a specific compound, 102 00:04:39,610 --> 00:04:41,681 you probably want a more complicated way 103 00:04:41,681 --> 00:04:42,430 to think about it. 104 00:04:42,430 --> 00:04:44,990 But if in general you just want to say, 105 00:04:44,990 --> 00:04:48,880 why can some cobalt complexes can be so many colors? 106 00:04:48,880 --> 00:04:51,700 Crystal field theory works really well for that. 107 00:04:51,700 --> 00:04:54,430 All right, so Crystal field theory. 108 00:04:54,430 --> 00:04:57,730 Very simple idea behind this. 109 00:04:57,730 --> 00:04:59,380 It's almost disappointing, I think. 110 00:04:59,380 --> 00:04:59,980 But it's OK. 111 00:04:59,980 --> 00:05:01,960 You can go, yeah we're studying, you know, 112 00:05:01,960 --> 00:05:03,670 Crystal field theory in class. 113 00:05:03,670 --> 00:05:06,190 Yeah, you don't have to tell people that it's 114 00:05:06,190 --> 00:05:08,450 a really, very simple idea. 115 00:05:08,450 --> 00:05:12,310 So the idea is that the ligands are negative charges. 116 00:05:12,310 --> 00:05:15,550 They're like this big blob of negativity. 117 00:05:15,550 --> 00:05:19,570 And those ligands, with their lone pairs, 118 00:05:19,570 --> 00:05:21,310 their negativeness or negative charge-- 119 00:05:21,310 --> 00:05:24,970 they got those extra lone pair electrons-- are going to be 120 00:05:24,970 --> 00:05:28,780 repulsive to those d orbitals. 121 00:05:28,780 --> 00:05:30,330 Negative point charges, you bring 122 00:05:30,330 --> 00:05:34,380 a d orbital, And a lone pair, and there's some repulsion. 123 00:05:34,380 --> 00:05:36,090 That's basically it. 124 00:05:36,090 --> 00:05:38,160 Negative point charge repulsion. 125 00:05:38,160 --> 00:05:39,930 That's all that you have to think about 126 00:05:39,930 --> 00:05:41,430 with Crystal field theory. 127 00:05:41,430 --> 00:05:45,000 So it sounds really impressive to tell people you're 128 00:05:45,000 --> 00:05:47,190 doing Crystal field theory. 129 00:05:47,190 --> 00:05:50,460 And you can neglect to mention that it's just 130 00:05:50,460 --> 00:05:54,090 a really very, very simple idea that, sort of, negative charges 131 00:05:54,090 --> 00:05:54,810 repel each other. 132 00:05:54,810 --> 00:05:56,395 That's really all it is. 133 00:05:56,395 --> 00:05:58,020 All right, so we're going to talk first 134 00:05:58,020 --> 00:06:00,240 about the octahedral case. 135 00:06:00,240 --> 00:06:02,820 And then we're going to get into some other geometries 136 00:06:02,820 --> 00:06:05,010 on Friday, so that's going to be exciting. 137 00:06:05,010 --> 00:06:07,678 But here's our octahedral molecule. 138 00:06:10,290 --> 00:06:14,580 And here we have it, here. 139 00:06:14,580 --> 00:06:19,140 And I can think about the metal in the middle, M to the N plus. 140 00:06:19,140 --> 00:06:23,100 So this just indicates it's any metal and to the oxidation 141 00:06:23,100 --> 00:06:24,480 number. 142 00:06:24,480 --> 00:06:26,400 And the black balls, here, are the ligands 143 00:06:26,400 --> 00:06:29,470 and we can think of those as negative charges. 144 00:06:29,470 --> 00:06:35,970 So here, we have drawn sort of this octohedral shape 145 00:06:35,970 --> 00:06:38,490 around the metal in the middle. 146 00:06:38,490 --> 00:06:40,500 And we can think about these NH3 groups 147 00:06:40,500 --> 00:06:41,990 as these negative point charges. 148 00:06:41,990 --> 00:06:45,430 So these dots here are negative point charges. 149 00:06:45,430 --> 00:06:47,940 And so now if we think about the shapes of the d orbitals 150 00:06:47,940 --> 00:06:52,240 again, that we just looked at, we can look over here and say, 151 00:06:52,240 --> 00:06:55,552 wow, some of those ligands that are those negative point 152 00:06:55,552 --> 00:06:59,250 charges are basically right there up 153 00:06:59,250 --> 00:07:01,020 against that d orbital. 154 00:07:01,020 --> 00:07:03,960 Pointing directly toward the d orbital. 155 00:07:03,960 --> 00:07:05,880 So that's going to be pretty repulsive. 156 00:07:05,880 --> 00:07:09,690 The point charge is right there next to the d orbital. 157 00:07:09,690 --> 00:07:12,580 This also has a point charge kind of right toward it 158 00:07:12,580 --> 00:07:14,130 along z. 159 00:07:14,130 --> 00:07:18,670 But these, the point charges, are on axis. 160 00:07:18,670 --> 00:07:22,470 Octahedral, you have your ligands along z, 161 00:07:22,470 --> 00:07:24,840 along x, and along y. 162 00:07:24,840 --> 00:07:28,260 But these sets of orbitals, the negative point charges, 163 00:07:28,260 --> 00:07:30,930 aren't pointing directly at the d orbitals. 164 00:07:30,930 --> 00:07:32,310 So one could think about the fact 165 00:07:32,310 --> 00:07:35,820 that these are not going to be not as much repulsion. 166 00:07:35,820 --> 00:07:37,470 This is a lot of repulsion. 167 00:07:37,470 --> 00:07:40,770 All right, so let's go through orbital set by orbital set 168 00:07:40,770 --> 00:07:44,250 and consider how repulsive it's going to be 169 00:07:44,250 --> 00:07:46,740 compared to the other orbitals. 170 00:07:46,740 --> 00:07:51,110 OK, so if we look over here at the octahedral case-- 171 00:07:51,110 --> 00:07:53,844 and I have both, these drawings were on the first page 172 00:07:53,844 --> 00:07:54,510 of your handout. 173 00:07:54,510 --> 00:07:56,580 This is on the second page. 174 00:07:56,580 --> 00:07:57,830 But you can think about them. 175 00:07:57,830 --> 00:07:59,790 Here it's drawn more where they're all 176 00:07:59,790 --> 00:08:01,590 drawn kind of the same way. 177 00:08:01,590 --> 00:08:04,260 Here it's sort of moved a little so you can see better. 178 00:08:04,260 --> 00:08:07,080 So we can keep both of these in mind. 179 00:08:07,080 --> 00:08:10,320 So, again, the negative point charges around the orbitals 180 00:08:10,320 --> 00:08:10,890 here. 181 00:08:10,890 --> 00:08:13,320 And on these drawings, I have these little negative signs 182 00:08:13,320 --> 00:08:17,527 pointing in to give you a sense of where those negative point 183 00:08:17,527 --> 00:08:19,620 charge ligands are coming. 184 00:08:19,620 --> 00:08:23,670 So we have our dz2 and we can see the negative point charge 185 00:08:23,670 --> 00:08:27,120 right toward this maximum amplitude along z. 186 00:08:27,120 --> 00:08:29,170 So that's going to be repulsive. 187 00:08:29,170 --> 00:08:34,710 Dx2, y2, same thing, point charges right toward these. 188 00:08:34,710 --> 00:08:41,130 So the ligands point directly at dz2 and dx2 minus y2. 189 00:08:41,130 --> 00:08:44,110 So there's a large repulsion there. 190 00:08:44,110 --> 00:08:47,310 And, in this particular case, in the octahedral case, 191 00:08:47,310 --> 00:08:51,660 what turns out to be true, both of these are stabilized. 192 00:08:51,660 --> 00:08:54,900 And they're destabilized, actually, by the same amount. 193 00:08:54,900 --> 00:08:58,170 And so that means that they have the same energy, which 194 00:08:58,170 --> 00:09:00,120 we learned before, means that there-- you 195 00:09:00,120 --> 00:09:03,000 could say they're degenerate with respect to each other. 196 00:09:03,000 --> 00:09:06,120 So both of these, big repulsion. 197 00:09:06,120 --> 00:09:10,890 Both are destabilized by those negative charges, 198 00:09:10,890 --> 00:09:12,900 by the same amount. 199 00:09:12,900 --> 00:09:16,950 And you have much more repulsion, and much more 200 00:09:16,950 --> 00:09:20,670 destabilization, for these two orbitals compared 201 00:09:20,670 --> 00:09:22,770 to the other set of orbitals. 202 00:09:22,770 --> 00:09:25,870 The ones that are 45 degrees off axis. 203 00:09:25,870 --> 00:09:27,660 So now, let's look at these and look 204 00:09:27,660 --> 00:09:30,150 at where the point charges are. 205 00:09:30,150 --> 00:09:32,214 So this is the picture in your handout. 206 00:09:32,214 --> 00:09:33,630 I just kind of put these up there, 207 00:09:33,630 --> 00:09:37,200 too, so you can think about where those point charges are 208 00:09:37,200 --> 00:09:39,420 for octahedral geometry. 209 00:09:39,420 --> 00:09:41,790 So the ligands, again now, are not 210 00:09:41,790 --> 00:09:46,050 pointing right at the orbitals. 211 00:09:46,050 --> 00:09:47,820 They're off axis. 212 00:09:47,820 --> 00:09:51,180 Because of ligands are on axis, and the orbitals are off axis, 213 00:09:51,180 --> 00:09:53,470 and they're not directly pointing toward each other. 214 00:09:53,470 --> 00:09:55,944 And so this is a lot less repulsive 215 00:09:55,944 --> 00:09:57,360 than the other situation where you 216 00:09:57,360 --> 00:09:59,340 have the ligands and the orbitals, 217 00:09:59,340 --> 00:10:02,440 both on axis, pointing right toward each other. 218 00:10:02,440 --> 00:10:05,340 So now, this is why it's important to know which 219 00:10:05,340 --> 00:10:08,894 orbitals are 45 degree off axis because we, now, 220 00:10:08,894 --> 00:10:10,560 can think about the fact that there will 221 00:10:10,560 --> 00:10:13,680 be less repulsion in this case. 222 00:10:13,680 --> 00:10:20,790 So, we can say then, that the xy, xz, and yz orbitals 223 00:10:20,790 --> 00:10:28,560 are stabilized compared to dz2 and dx2 minus y2 orbitals. 224 00:10:28,560 --> 00:10:31,810 And they're also stabilized by the same amount. 225 00:10:31,810 --> 00:10:33,810 So these are also degenerate. 226 00:10:33,810 --> 00:10:37,400 With respect to each other, they have the same energy. 227 00:10:37,400 --> 00:10:41,490 All right, so we have these now two sets of orbital types. 228 00:10:41,490 --> 00:10:44,460 Two orbitals that are destabilized, 229 00:10:44,460 --> 00:10:48,630 and three orbitals that are stabilized, compared to them. 230 00:10:48,630 --> 00:10:55,160 So now let's draw what's known as an Octahedral Crystal Field 231 00:10:55,160 --> 00:10:59,160 Splitting Diagram and think about what's happening. 232 00:10:59,160 --> 00:11:01,150 So, I have some over there. 233 00:11:01,150 --> 00:11:02,630 Ignore those for now. 234 00:11:02,630 --> 00:11:05,550 I'm going to draw one over here. 235 00:11:05,550 --> 00:11:09,080 So first, we have energy going up. 236 00:11:09,080 --> 00:11:13,070 And we have a situation we first want to think about. 237 00:11:13,070 --> 00:11:17,510 What would be the case, say, if you had ligands everywhere? 238 00:11:17,510 --> 00:11:21,230 Not just on the axis, not octahedral geometry, 239 00:11:21,230 --> 00:11:22,710 but just everywhere. 240 00:11:22,710 --> 00:11:25,160 So if you had ligands everywhere, 241 00:11:25,160 --> 00:11:28,440 you would have your 5 d orbitals, 242 00:11:28,440 --> 00:11:29,810 all would have the same energy. 243 00:11:29,810 --> 00:11:31,940 Because all of them-- there's ligands everywhere-- 244 00:11:31,940 --> 00:11:33,740 all of them would be experiencing 245 00:11:33,740 --> 00:11:36,320 the same amount of repulsion. 246 00:11:36,320 --> 00:11:42,060 So this would be the case for a Spherical Crystal Field. 247 00:11:47,180 --> 00:11:52,400 And I like to think about this with this prop. 248 00:11:52,400 --> 00:11:54,006 I had this before as an s orbital. 249 00:11:54,006 --> 00:11:55,380 It's convenient for that as well. 250 00:11:55,380 --> 00:11:59,540 But, really, what it is, is a Hypothetical Spherical Crystal 251 00:11:59,540 --> 00:12:00,890 Field. 252 00:12:00,890 --> 00:12:03,320 Because these are all little ligands. 253 00:12:03,320 --> 00:12:05,750 And you can see these little ligands are 254 00:12:05,750 --> 00:12:08,120 completely symmetric around. 255 00:12:08,120 --> 00:12:09,590 And if you feel sort of the inside, 256 00:12:09,590 --> 00:12:10,870 there's something in there. 257 00:12:10,870 --> 00:12:13,220 Well that, of course, is a metal ion. 258 00:12:13,220 --> 00:12:15,830 And these ligands are completely around. 259 00:12:15,830 --> 00:12:19,250 So all the d orbitals are equally 260 00:12:19,250 --> 00:12:22,340 feeling the repulsive effects of these ligands. 261 00:12:22,340 --> 00:12:25,190 And so they all have the same energy 262 00:12:25,190 --> 00:12:26,840 in this hypothetical case. 263 00:12:26,840 --> 00:12:29,312 I was so excited when I found this at CVS. 264 00:12:29,312 --> 00:12:30,770 And I went up and I was, like, wow, 265 00:12:30,770 --> 00:12:34,430 you sell hypothetical spherical crystal fields here. 266 00:12:34,430 --> 00:12:36,410 And the person was not amused. 267 00:12:36,410 --> 00:12:42,470 OK, so now what happens-- because this is not the case. 268 00:12:42,470 --> 00:12:43,267 This doesn't exist. 269 00:12:43,267 --> 00:12:44,350 This is just hypothetical. 270 00:12:44,350 --> 00:12:47,360 It looks like it exists, but it doesn't. 271 00:12:47,360 --> 00:12:49,410 This is what really exists. 272 00:12:49,410 --> 00:12:51,230 You have certain geometries. 273 00:12:51,230 --> 00:12:53,120 The ligands come together with the metal 274 00:12:53,120 --> 00:12:55,160 and form particular geometries. 275 00:12:55,160 --> 00:12:57,860 And we already talked about what those geometries are. 276 00:12:57,860 --> 00:12:59,750 There's not a whole lot of variation. 277 00:12:59,750 --> 00:13:01,580 We get the same kinds of geometries. 278 00:13:01,580 --> 00:13:04,700 And octahedral is the most common geometry 279 00:13:04,700 --> 00:13:06,650 for a transition metal complex. 280 00:13:06,650 --> 00:13:08,250 So what's going to happen here? 281 00:13:08,250 --> 00:13:12,860 So, the ligands will now split the energy of the d orbitals. 282 00:13:12,860 --> 00:13:16,460 And three of them are going to go down in energy. 283 00:13:16,460 --> 00:13:21,110 They're going to be stabilized compared to the two that 284 00:13:21,110 --> 00:13:24,560 go up in energy. 285 00:13:24,560 --> 00:13:28,360 So the three that go-- are stabilized again, 286 00:13:28,360 --> 00:13:36,195 are dxy, dyz, and dxz. 287 00:13:36,195 --> 00:13:38,570 If you can't read this, it all should be in your handout. 288 00:13:38,570 --> 00:13:41,020 So it's OK, you don't have to read my handwriting. 289 00:13:41,020 --> 00:13:44,810 And just kind of-- just follow along in your notes. 290 00:13:44,810 --> 00:13:47,730 And then the ones that have the most repulsion are 291 00:13:47,730 --> 00:13:54,770 dx2 minus y2 and dz2 up here. 292 00:13:54,770 --> 00:13:57,150 All right, so two go up and energy. 293 00:13:57,150 --> 00:13:58,670 There's more repulsion. 294 00:13:58,670 --> 00:14:01,010 Three go down in energy. 295 00:14:01,010 --> 00:14:04,110 And instead of writing all of those d's 296 00:14:04,110 --> 00:14:07,790 and x's and y's, they're little abbreviations that people use. 297 00:14:07,790 --> 00:14:14,850 So they call these two orbitals-- the eg orbitals. 298 00:14:14,850 --> 00:14:17,630 So those are the ones that are destabilized. 299 00:14:17,630 --> 00:14:19,760 And the ones that are stabilized are 300 00:14:19,760 --> 00:14:23,510 called t2g orbitals, which is going 301 00:14:23,510 --> 00:14:27,350 to make our nomenclature easier later on. 302 00:14:27,350 --> 00:14:29,180 OK, these two again. 303 00:14:29,180 --> 00:14:32,034 Same energy I tried to draw a straight line between them. 304 00:14:32,034 --> 00:14:33,950 They're degenerate with respect to each other. 305 00:14:33,950 --> 00:14:37,040 These three of the same energy, again, degenerate with respect 306 00:14:37,040 --> 00:14:38,180 to each other. 307 00:14:38,180 --> 00:14:43,400 And then the difference of how much it's being split. 308 00:14:43,400 --> 00:14:46,580 This energy difference has a special name. 309 00:14:46,580 --> 00:14:49,610 It's sort of this delta sub o. 310 00:14:49,610 --> 00:14:51,960 And this is the octahedral. 311 00:14:54,970 --> 00:14:56,390 And that's the o. 312 00:14:56,390 --> 00:14:58,730 The o is octahedral. 313 00:14:58,730 --> 00:15:10,370 Crystal field splitting energy because it's 314 00:15:10,370 --> 00:15:13,280 the energy that shows the splitting of the crystal field. 315 00:15:13,280 --> 00:15:16,620 So that's at least a good name for it. 316 00:15:16,620 --> 00:15:21,020 All right, now, overall this energy 317 00:15:21,020 --> 00:15:23,310 is going to be conserved. 318 00:15:23,310 --> 00:15:27,550 So the orbitals that go-- that are destabilized-- 319 00:15:27,550 --> 00:15:30,270 and two go up and three go down. 320 00:15:30,270 --> 00:15:38,420 So we can also put that the two that go up, go up by 3/5 times 321 00:15:38,420 --> 00:15:41,780 the octahedral splitting energy. 322 00:15:41,780 --> 00:15:45,670 And the three that go down-- are stabilized-- 323 00:15:45,670 --> 00:15:49,750 go down by minus 2/5 times the octahedral crystal 324 00:15:49,750 --> 00:15:51,010 field, splitting energy. 325 00:15:51,010 --> 00:15:52,330 So this is why I have it in your notes, 326 00:15:52,330 --> 00:15:54,413 because you can't really read my writing too well. 327 00:15:54,413 --> 00:15:59,020 So two go-- are destabilized, up by 3/5. 328 00:15:59,020 --> 00:16:03,910 Three, or stabilized, down by 2/5 in energy. 329 00:16:03,910 --> 00:16:08,770 All right, so now what controls the overall size 330 00:16:08,770 --> 00:16:10,744 of this splitting energy? 331 00:16:10,744 --> 00:16:11,410 How do you know? 332 00:16:11,410 --> 00:16:12,727 Is it a small splitting? 333 00:16:12,727 --> 00:16:14,560 Is this, you know, should I have drawn this, 334 00:16:14,560 --> 00:16:15,768 that they're just a tiny bit? 335 00:16:15,768 --> 00:16:18,760 Or is it, like, could it be a really large splitting? 336 00:16:18,760 --> 00:16:21,920 What determines the splitting? 337 00:16:21,920 --> 00:16:25,870 Or The magnitude of this splitting energy. 338 00:16:25,870 --> 00:16:29,920 So what determines that are the nature of ligands. 339 00:16:29,920 --> 00:16:34,330 So some ligands are really repulsive. 340 00:16:34,330 --> 00:16:35,740 Big splitting. 341 00:16:35,740 --> 00:16:38,740 Others-- eh-- you barely notice they're there. 342 00:16:38,740 --> 00:16:40,000 Very little splitting. 343 00:16:40,000 --> 00:16:42,550 There's always some splitting. 344 00:16:42,550 --> 00:16:44,590 But it can be different. 345 00:16:44,590 --> 00:16:47,470 So the relative ability of a ligand 346 00:16:47,470 --> 00:16:50,950 to split the crystal field gives rise 347 00:16:50,950 --> 00:16:54,610 to what's known as the Spectrochemical Series. 348 00:16:54,610 --> 00:16:57,760 So it's the relative ability of common ligands 349 00:16:57,760 --> 00:17:02,020 to split the energies of these d orbitals. 350 00:17:02,020 --> 00:17:04,869 And this is what gives rise to these beautiful colors. 351 00:17:04,869 --> 00:17:08,560 So all of those colors are possible from cobalt compounds. 352 00:17:08,560 --> 00:17:10,150 Every single one of them. 353 00:17:10,150 --> 00:17:12,520 Because different ligands will split the energy 354 00:17:12,520 --> 00:17:16,460 different amounts, giving rise to those different colors. 355 00:17:16,460 --> 00:17:19,750 So we have what's known as Strong field ligands. 356 00:17:19,750 --> 00:17:22,810 And as that name would suggest, Strong field ligands 357 00:17:22,810 --> 00:17:24,310 are going to have a large splitting. 358 00:17:24,310 --> 00:17:25,780 They're very strong. 359 00:17:25,780 --> 00:17:29,530 They split to a large degree. 360 00:17:29,530 --> 00:17:35,110 And we have Weak field ligands. 361 00:17:35,110 --> 00:17:37,090 Weak field don't cause much of a splitting. 362 00:17:37,090 --> 00:17:43,390 It's a small delta sub o, small octahedral crystal 363 00:17:43,390 --> 00:17:46,780 field splitting energy. 364 00:17:46,780 --> 00:17:48,970 All right, so which common ligands 365 00:17:48,970 --> 00:17:52,780 fall into which categories? 366 00:17:52,780 --> 00:17:55,750 Here is the list that we talk about pretty much 367 00:17:55,750 --> 00:17:56,540 in this class. 368 00:17:56,540 --> 00:17:58,630 I don't think there are any other ones. 369 00:17:58,630 --> 00:18:00,970 So what I will put on your equation sheet-- 370 00:18:00,970 --> 00:18:02,390 your equation sheet for exam four 371 00:18:02,390 --> 00:18:03,880 is lots of cool, interesting things 372 00:18:03,880 --> 00:18:06,310 that were not in the other equation sheets. 373 00:18:06,310 --> 00:18:08,220 And I will tell you which are weak field, 374 00:18:08,220 --> 00:18:09,970 and which are strong field, but I will not 375 00:18:09,970 --> 00:18:12,816 tell you that weak field means that it's a small splitting. 376 00:18:12,816 --> 00:18:14,440 That's something that you need to know. 377 00:18:14,440 --> 00:18:16,960 Or that strong field means it's a large splitting. 378 00:18:16,960 --> 00:18:19,360 But I will tell you that your halides down here 379 00:18:19,360 --> 00:18:21,520 are weak field ligands. 380 00:18:21,520 --> 00:18:24,370 Water and hydroxide are sort of in the middle. 381 00:18:24,370 --> 00:18:26,410 And they can have all sorts of different colors 382 00:18:26,410 --> 00:18:29,110 when they're bound to coordination complexes. 383 00:18:29,110 --> 00:18:30,640 So they're sort of intermediate. 384 00:18:30,640 --> 00:18:33,640 And then your strong field ligands-- with your strongest 385 00:18:33,640 --> 00:18:34,900 being cyanide. 386 00:18:34,900 --> 00:18:37,020 Very strong field ligand. 387 00:18:37,020 --> 00:18:41,890 All right, so, if your metal has a weak field, 388 00:18:41,890 --> 00:18:44,380 intermediate field, or strong field ligand, 389 00:18:44,380 --> 00:18:46,030 it can have very different properties. 390 00:18:46,030 --> 00:18:48,190 Especially very different colors. 391 00:18:48,190 --> 00:18:51,310 Also, it could be paramagnetic or diamagnetic, 392 00:18:51,310 --> 00:18:53,680 depending on this. 393 00:18:53,680 --> 00:18:56,980 So let's take a look at two different iron complexes. 394 00:18:56,980 --> 00:19:00,490 We have iron with six waters, with a plus 3 395 00:19:00,490 --> 00:19:04,500 charge, and iron with cyanide, with six cyanides 396 00:19:04,500 --> 00:19:05,860 and a minus 3. 397 00:19:05,860 --> 00:19:08,860 So the first thing we have to do is figure out 398 00:19:08,860 --> 00:19:11,980 the oxidation number of the iron and the d count. 399 00:19:11,980 --> 00:19:13,650 And that's our first clicker question. 400 00:19:34,619 --> 00:19:36,410 All right, let's just take 10 more seconds. 401 00:19:55,450 --> 00:19:58,110 OK. 402 00:19:58,110 --> 00:19:58,660 There you go. 403 00:19:58,660 --> 00:19:59,790 There's the right one. 404 00:19:59,790 --> 00:20:01,360 A little more people say that. 405 00:20:01,360 --> 00:20:02,100 All right. 406 00:20:02,100 --> 00:20:04,570 So, let's take a look at this. 407 00:20:04,570 --> 00:20:06,240 And you will get used to thinking 408 00:20:06,240 --> 00:20:09,210 about what the charges are on the various ligands. 409 00:20:09,210 --> 00:20:13,260 So here, we know that the overall charge 410 00:20:13,260 --> 00:20:17,460 has to be the same as the overall charge on the complex. 411 00:20:17,460 --> 00:20:19,180 Water is neutral. 412 00:20:19,180 --> 00:20:22,500 And so that means this iron has to be plus 3. 413 00:20:22,500 --> 00:20:24,840 Cyanide has a minus charge, and you 414 00:20:24,840 --> 00:20:27,720 may have noticed that in the list of ligands, 415 00:20:27,720 --> 00:20:30,390 that it was cn minus. 416 00:20:30,390 --> 00:20:33,090 That when I just showed you the strong field ligands. 417 00:20:33,090 --> 00:20:35,170 So there's six minus ones. 418 00:20:35,170 --> 00:20:37,410 And so it's also plus 3, to give you 419 00:20:37,410 --> 00:20:40,320 an overall charge of minus 3. 420 00:20:40,320 --> 00:20:43,370 And as you do these problems, and problem sets, 421 00:20:43,370 --> 00:20:45,150 you'll become very familiar with what 422 00:20:45,150 --> 00:20:47,280 the charges of the different ligands are. 423 00:20:47,280 --> 00:20:50,760 So overall, plus 3, 8 minus 3, is 5. 424 00:20:50,760 --> 00:20:51,915 Is a d5 system. 425 00:20:54,812 --> 00:20:56,270 So the next thing we're going to do 426 00:20:56,270 --> 00:20:58,790 is we're going to draw our octahedral crystal field 427 00:20:58,790 --> 00:21:01,680 splitting diagrams and place electrons. 428 00:21:01,680 --> 00:21:08,720 And I already have, over here, a starting place for those. 429 00:21:08,720 --> 00:21:13,160 So we're doing here our d5 system. 430 00:21:13,160 --> 00:21:17,720 And we have a diagram with a small splitting 431 00:21:17,720 --> 00:21:20,340 and one with a large splitting. 432 00:21:20,340 --> 00:21:22,260 So with the small splitting, is that 433 00:21:22,260 --> 00:21:25,617 going to be a weak field or a strong field? 434 00:21:25,617 --> 00:21:26,700 That will be a weak field. 435 00:21:29,240 --> 00:21:32,990 And when we have a large splitting, 436 00:21:32,990 --> 00:21:37,120 that is a strong field 437 00:21:37,120 --> 00:21:41,030 OK, so which of our two compounds 438 00:21:41,030 --> 00:21:43,860 is going to be the weak field compound? 439 00:21:43,860 --> 00:21:45,120 And which will be the strong? 440 00:21:45,120 --> 00:21:46,800 Let's do strong first. 441 00:21:46,800 --> 00:21:50,660 Which one has a strong field ligand? 442 00:21:50,660 --> 00:21:52,220 Cyanide one. 443 00:21:52,220 --> 00:22:01,400 So this one is going to be our cyanide complex because it 444 00:22:01,400 --> 00:22:03,500 has the strong field. 445 00:22:03,500 --> 00:22:05,580 And so this one would be the water. 446 00:22:05,580 --> 00:22:06,750 Water's intermediate. 447 00:22:06,750 --> 00:22:09,600 So you kind of have to see what the comparison is first 448 00:22:09,600 --> 00:22:10,460 before you decide. 449 00:22:13,390 --> 00:22:17,370 Oops, six bracket 3 plus. 450 00:22:17,370 --> 00:22:19,080 OK, so here we have water. 451 00:22:19,080 --> 00:22:20,450 There, we have cyanide. 452 00:22:20,450 --> 00:22:24,050 So a weak, or intermediate field, versus a strong field. 453 00:22:24,050 --> 00:22:27,572 All right, now we need to put electrons in here. 454 00:22:27,572 --> 00:22:28,405 So I have to decide. 455 00:22:28,405 --> 00:22:31,050 I have five electrons I'm going to play with. 456 00:22:31,050 --> 00:22:33,600 And I could put them in here. 457 00:22:33,600 --> 00:22:34,600 Let's just start here. 458 00:22:34,600 --> 00:22:36,570 Do one, two, three. 459 00:22:36,570 --> 00:22:39,630 Now the question is, where am I going to put four? 460 00:22:39,630 --> 00:22:42,330 Am I going to put four down here? 461 00:22:42,330 --> 00:22:44,180 Or put it up here? 462 00:22:44,180 --> 00:22:50,480 And so, here, it depends on, if I put it down here on pairing-- 463 00:22:50,480 --> 00:22:52,926 and, you know, the seats on the bus-- people 464 00:22:52,926 --> 00:22:54,300 don't really want to sit together 465 00:22:54,300 --> 00:22:55,341 if there are empty seats. 466 00:22:55,341 --> 00:22:58,110 Now there are empty seats up here. 467 00:22:58,110 --> 00:23:03,020 So, the question is, is it going to take more energy to pair? 468 00:23:03,020 --> 00:23:05,030 Or more energy to put it up here? 469 00:23:05,030 --> 00:23:09,530 Now, if this is a weak field, which it is, 470 00:23:09,530 --> 00:23:11,940 then that's not all that far away. 471 00:23:11,940 --> 00:23:13,940 You get on a bus and you see a seat in the back. 472 00:23:13,940 --> 00:23:15,481 You'd rather sit up front, but you're 473 00:23:15,481 --> 00:23:18,230 like, than you have to sit with someone, so you go to the back. 474 00:23:18,230 --> 00:23:20,660 So that's what happens with a weak field. 475 00:23:20,660 --> 00:23:24,240 The other energy levels are just not that far away, 476 00:23:24,240 --> 00:23:26,300 so you go up there. 477 00:23:26,300 --> 00:23:30,270 And if I kind of put this up-- move it up 478 00:23:30,270 --> 00:23:34,590 for just a second-- and then I'll say, so this rule here, 479 00:23:34,590 --> 00:23:36,870 and I'm going to kind of cover this up again. 480 00:23:36,870 --> 00:23:38,820 But maybe I'll just put it down here. 481 00:23:38,820 --> 00:23:39,920 This is in your notes. 482 00:23:39,920 --> 00:23:44,340 So here, the octahedral crystal field splitting energy 483 00:23:44,340 --> 00:23:50,588 is less than we call PE, which is pairing energy. 484 00:23:53,900 --> 00:23:57,910 So, it's not that far away. 485 00:23:57,910 --> 00:24:00,230 Just put them singly, to the full extent 486 00:24:00,230 --> 00:24:04,590 possible, before you pair. 487 00:24:04,590 --> 00:24:07,550 So that's what happens with a weak field. 488 00:24:07,550 --> 00:24:10,110 And we also can think about how we're putting 489 00:24:10,110 --> 00:24:11,900 in our electrons parallel. 490 00:24:11,900 --> 00:24:15,410 We're not putting them in all sorts of different directions. 491 00:24:15,410 --> 00:24:18,037 And we're not-- if we do pair-- we're going to not pair-- 492 00:24:18,037 --> 00:24:18,870 we're going to pair. 493 00:24:18,870 --> 00:24:20,390 So one's up, one's down. 494 00:24:20,390 --> 00:24:22,400 So all the rules that we learned earlier 495 00:24:22,400 --> 00:24:23,400 are going to apply here. 496 00:24:23,400 --> 00:24:25,650 So this is good, good review. 497 00:24:25,650 --> 00:24:32,734 So now, in this case, we can put in our first three electrons. 498 00:24:32,734 --> 00:24:33,650 And what do you think? 499 00:24:33,650 --> 00:24:35,180 Do you think I'm going to pair? 500 00:24:35,180 --> 00:24:40,160 Or do you think I'm going to go up there? 501 00:24:40,160 --> 00:24:41,580 What do you think? 502 00:24:41,580 --> 00:24:42,270 I'm going pair. 503 00:24:42,270 --> 00:24:44,300 Yeah, I'm definitely going to pair. 504 00:24:44,300 --> 00:24:46,960 So I'm going to put my other two over here. 505 00:24:46,960 --> 00:24:51,500 So in this case, the pair-- the octahedral crystal field 506 00:24:51,500 --> 00:24:53,130 splitting energy-- it's so much fun 507 00:24:53,130 --> 00:24:55,430 to say that so many times-- is greater 508 00:24:55,430 --> 00:24:57,270 than the pairing energy. 509 00:24:57,270 --> 00:24:59,850 And, so, in this case, there might be empty seats. 510 00:24:59,850 --> 00:25:01,630 But maybe it's a long train. 511 00:25:01,630 --> 00:25:05,580 And there is-- you can sit in car one with someone else, 512 00:25:05,580 --> 00:25:07,050 or carry all your luggage. 513 00:25:07,050 --> 00:25:08,390 Why did you bring so much? 514 00:25:08,390 --> 00:25:10,160 You're just going home for Thanksgiving. 515 00:25:10,160 --> 00:25:13,590 All the way, 23 cars later, to an empty seat in the back. 516 00:25:13,590 --> 00:25:15,460 You're just not going to do it. 517 00:25:15,460 --> 00:25:17,300 You don't have enough energy. 518 00:25:17,300 --> 00:25:20,210 You'd rather sit with somebody up front. 519 00:25:20,210 --> 00:25:23,010 So how you put in electrons depends if it's 520 00:25:23,010 --> 00:25:24,600 a weak field or strong field. 521 00:25:24,600 --> 00:25:29,510 It depends on whether it takes just a little bit of energy, 522 00:25:29,510 --> 00:25:30,980 and it's worse to pair. 523 00:25:30,980 --> 00:25:32,850 Or takes a huge amount of energy. 524 00:25:32,850 --> 00:25:35,630 There's a big splitting, a really strong field. 525 00:25:35,630 --> 00:25:37,940 And in that case, you're going to pair first. 526 00:25:37,940 --> 00:25:40,590 And you're only going to put electrons up here when 527 00:25:40,590 --> 00:25:43,810 you're completely done here. 528 00:25:43,810 --> 00:25:48,250 All right, so now we have placed our electrons. 529 00:25:48,250 --> 00:25:50,380 We've talked about pairing energy. 530 00:25:50,380 --> 00:25:53,980 And we've talked about the weak and strong fields. 531 00:25:53,980 --> 00:25:56,560 And now we can talk about some notation. 532 00:25:56,560 --> 00:25:58,370 Because there's always notation. 533 00:25:58,370 --> 00:26:01,270 So this is what we've done already. 534 00:26:01,270 --> 00:26:07,450 And now we're going to do step E, which is to our d to the n 535 00:26:07,450 --> 00:26:09,400 electron configurations. 536 00:26:09,400 --> 00:26:13,630 Every diagram, there's different configurations every time. 537 00:26:13,630 --> 00:26:17,560 So this one we do using those little kind of cool terms 538 00:26:17,560 --> 00:26:19,400 I told you about. 539 00:26:19,400 --> 00:26:24,160 So instead of writing, I have one electron in dxy, 540 00:26:24,160 --> 00:26:28,900 one electron in dxz, and one electron in dyz, 541 00:26:28,900 --> 00:26:34,750 I can just say, I have three in the t2g set of orbitals 542 00:26:34,750 --> 00:26:36,800 that is a lot more convenient. 543 00:26:36,800 --> 00:26:39,760 So you would just say t2g3. 544 00:26:39,760 --> 00:26:41,420 And I have two up here. 545 00:26:41,420 --> 00:26:43,780 So EG2. 546 00:26:43,780 --> 00:26:45,310 And that's how you would do this. 547 00:26:45,310 --> 00:26:48,310 I think this is our last configuration for electrons 548 00:26:48,310 --> 00:26:53,390 in a diagram that you're going to be learning. 549 00:26:53,390 --> 00:26:54,510 There's a lot of them. 550 00:26:54,510 --> 00:26:57,130 OK, so then over here, we would just 551 00:26:57,130 --> 00:27:00,310 say we have five, all in the lower energy 552 00:27:00,310 --> 00:27:03,360 set, all in our t2g. 553 00:27:03,360 --> 00:27:08,740 All right, one other thing, part F that you can be asked about. 554 00:27:08,740 --> 00:27:14,830 Which is the crystal field stabilization energy. 555 00:27:14,830 --> 00:27:21,100 Not to be confused with the crystal field splitting energy. 556 00:27:21,100 --> 00:27:22,780 They both start with an s. 557 00:27:22,780 --> 00:27:25,660 So I don't know why you wouldn't be confused by that. 558 00:27:25,660 --> 00:27:29,440 But if you can try to remember it, that would be awesome. 559 00:27:29,440 --> 00:27:33,820 It's often abbreviated, CFSE. 560 00:27:33,820 --> 00:27:37,420 And this is the energy change that's 561 00:27:37,420 --> 00:27:41,050 due to going from this hypothetical spherical crystal 562 00:27:41,050 --> 00:27:44,560 field, where all the d orbitals have the same energy. 563 00:27:44,560 --> 00:27:46,330 And if you put your electrons in here, 564 00:27:46,330 --> 00:27:50,590 where they'd all have the same energy, to the diff energy 565 00:27:50,590 --> 00:27:53,290 difference, when you're placing energies-- when you're placing 566 00:27:53,290 --> 00:27:56,830 the electrons in lower energy orbitals or higher energy 567 00:27:56,830 --> 00:27:57,550 orbitals. 568 00:27:57,550 --> 00:28:00,750 So you're thinking about how much more stabilized 569 00:28:00,750 --> 00:28:04,370 is the system if all of the electrons are down here. 570 00:28:04,370 --> 00:28:06,010 That's going to be stabilized compared 571 00:28:06,010 --> 00:28:07,330 to where they were here. 572 00:28:07,330 --> 00:28:09,610 But if a lot of them are up here, 573 00:28:09,610 --> 00:28:11,980 then there'd be less stabilization due 574 00:28:11,980 --> 00:28:13,660 to this splitting. 575 00:28:13,660 --> 00:28:18,250 All right, so let's look at how we would write that. 576 00:28:18,250 --> 00:28:23,350 So we have three electrons that are down in energy. 577 00:28:23,350 --> 00:28:27,250 And they are down in energy by minus 2/5 times 578 00:28:27,250 --> 00:28:31,490 the octahedral crystal field splitting energy. 579 00:28:31,490 --> 00:28:34,150 And that's because the overall energy is maintained. 580 00:28:34,150 --> 00:28:37,060 Three go down in energy, so that's minus 2. 581 00:28:37,060 --> 00:28:39,580 Two go up in energy, again, plus 3. 582 00:28:39,580 --> 00:28:42,880 And then we have two electrons up here. 583 00:28:42,880 --> 00:28:47,890 So 2 times plus 3/5, again times the octahedral crystal field 584 00:28:47,890 --> 00:28:49,430 splitting energy. 585 00:28:49,430 --> 00:28:52,930 And so overall, our stabilization is zero. 586 00:28:52,930 --> 00:28:55,240 There's no stabilization of this system, 587 00:28:55,240 --> 00:28:58,570 compared to the system here, because three electrons are 588 00:28:58,570 --> 00:29:01,030 down in energy, and two are up. 589 00:29:01,030 --> 00:29:03,730 All right, so now you might imagine 590 00:29:03,730 --> 00:29:06,820 that this is going to have some extra stabilization. 591 00:29:06,820 --> 00:29:08,500 And you would be right. 592 00:29:08,500 --> 00:29:10,160 So we would write this like this. 593 00:29:10,160 --> 00:29:12,880 We'd say there are five electrons down. 594 00:29:12,880 --> 00:29:16,070 Stabilized in the lower energy orbitals. 595 00:29:16,070 --> 00:29:20,320 So five times minus 2/5, times the optic single crystal field 596 00:29:20,320 --> 00:29:24,610 splitting energy, minus 10/5 times the octahedral crystal 597 00:29:24,610 --> 00:29:26,200 field splitting energy. 598 00:29:26,200 --> 00:29:29,470 And sometimes you'll also see, kind of a little truth, 599 00:29:29,470 --> 00:29:34,570 that there's also some energy kind of due to this pairing. 600 00:29:34,570 --> 00:29:39,910 So you might see an indication that there's pairing energy 601 00:29:39,910 --> 00:29:41,500 for two sets of electrons. 602 00:29:41,500 --> 00:29:42,880 So sometimes that's included. 603 00:29:42,880 --> 00:29:43,720 Sometimes it's not. 604 00:29:43,720 --> 00:29:45,880 The questions were asked to indicate, you know, 605 00:29:45,880 --> 00:29:48,130 how many of sets of electrons ended up 606 00:29:48,130 --> 00:29:51,970 being paired for that stabilization? 607 00:29:51,970 --> 00:29:55,630 All right, so we can think about, 608 00:29:55,630 --> 00:29:58,632 again, we have this nomenclature here. 609 00:29:58,632 --> 00:30:00,340 And we can think about the stabilization. 610 00:30:00,340 --> 00:30:03,100 So there's a big difference between these iron compounds. 611 00:30:03,100 --> 00:30:05,705 One, there's no stabilization due to the splitting. 612 00:30:05,705 --> 00:30:07,330 And the other one, there's quite a bit, 613 00:30:07,330 --> 00:30:09,430 because all the electrons ended down 614 00:30:09,430 --> 00:30:10,994 in the lower energy orbitals. 615 00:30:13,900 --> 00:30:16,780 So now it's time to try some of these on your own. 616 00:30:16,780 --> 00:30:19,510 See if you got the rules down. 617 00:30:19,510 --> 00:30:24,460 And let's try some clicker questions. 618 00:30:24,460 --> 00:30:25,690 Clicker question one. 619 00:30:48,520 --> 00:30:49,500 OK, 10 more seconds. 620 00:31:04,000 --> 00:31:05,810 All right, yes. 621 00:31:05,810 --> 00:31:11,150 So the trick here is to remind yourself what weak field meant. 622 00:31:11,150 --> 00:31:13,730 And in this case, if it's a weak field, that 623 00:31:13,730 --> 00:31:16,790 meant that you place all the electrons singly-- 624 00:31:16,790 --> 00:31:19,580 there are seven of them-- to the fullest extent possible 625 00:31:19,580 --> 00:31:20,390 before you pair. 626 00:31:20,390 --> 00:31:23,180 You still have to pair. 627 00:31:23,180 --> 00:31:25,580 But here you put more-- you filled these up 628 00:31:25,580 --> 00:31:26,870 before you paired. 629 00:31:26,870 --> 00:31:29,210 And this is a strong field diagram 630 00:31:29,210 --> 00:31:31,040 where you put-- you paired all of them 631 00:31:31,040 --> 00:31:33,500 possible before you put any of them up here. 632 00:31:33,500 --> 00:31:36,260 And to make it harder, I made-- drew them the same. 633 00:31:36,260 --> 00:31:37,790 So you have to really pay attention 634 00:31:37,790 --> 00:31:39,500 to what weak field meant. 635 00:31:39,500 --> 00:31:41,840 But this would be the version of the strong field. 636 00:31:41,840 --> 00:31:44,640 And this is just wrong. 637 00:31:44,640 --> 00:31:47,270 So, you wouldn't have more electrons 638 00:31:47,270 --> 00:31:50,120 up in the higher energy orbitals for really any reason 639 00:31:50,120 --> 00:31:51,250 whatsoever. 640 00:31:51,250 --> 00:31:54,324 OK, so let's try the next one. 641 00:32:12,960 --> 00:32:15,030 All right, let's just take 10 more seconds 642 00:32:15,030 --> 00:32:17,636 and we'll mention high spin and we'll do this problem. 643 00:32:29,140 --> 00:32:29,830 Yeah. 644 00:32:29,830 --> 00:32:31,121 People did very well with that. 645 00:32:31,121 --> 00:32:34,910 OK, so I forgot to mention that I ran out of room to draw. 646 00:32:34,910 --> 00:32:37,030 So I decided that was enough. 647 00:32:37,030 --> 00:32:39,940 So it's in your notes though, for here. 648 00:32:39,940 --> 00:32:44,620 And when you have a very small, weak field, 649 00:32:44,620 --> 00:32:48,640 and you end up putting all the electrons in singly, 650 00:32:48,640 --> 00:32:51,490 that is also known-- and I'll move this up a little 651 00:32:51,490 --> 00:32:57,080 bit-- as a high spin. 652 00:32:57,080 --> 00:33:00,730 And so you have a lot of unpaired electrons 653 00:33:00,730 --> 00:33:01,960 in this case. 654 00:33:01,960 --> 00:33:11,185 So that is the maximum number of unpaired electrons. 655 00:33:14,804 --> 00:33:16,720 And it's easier to remember because, you know, 656 00:33:16,720 --> 00:33:17,594 you have these spins. 657 00:33:17,594 --> 00:33:18,640 There's a lot of spins. 658 00:33:18,640 --> 00:33:22,540 There are a lot of single spins and they're also high up. 659 00:33:22,540 --> 00:33:26,410 And this is a low spin case. 660 00:33:26,410 --> 00:33:28,810 When you have a strong field. 661 00:33:28,810 --> 00:33:32,770 Because you like to pair first before putting them singly. 662 00:33:32,770 --> 00:33:36,970 So this is going to give you the minimum number 663 00:33:36,970 --> 00:33:41,462 of unpaired electrons. 664 00:33:47,080 --> 00:33:49,840 So high spin, weak field. 665 00:33:49,840 --> 00:33:53,380 Low spin often comes from a strong field. 666 00:33:53,380 --> 00:33:55,540 So it's about whether you have maximum number 667 00:33:55,540 --> 00:33:57,400 of unpaired electrons, which you do 668 00:33:57,400 --> 00:34:00,340 with weak field, high spin, minimum number. 669 00:34:00,340 --> 00:34:02,440 All right, so let's look at this one then. 670 00:34:02,440 --> 00:34:06,340 So it's a high field one. 671 00:34:06,340 --> 00:34:08,830 So that means that you're going to have the maximum number 672 00:34:08,830 --> 00:34:11,659 of unpaired electrons. 673 00:34:11,659 --> 00:34:14,620 So this would be diagram here. 674 00:34:14,620 --> 00:34:19,420 And I can put that over here. 675 00:34:19,420 --> 00:34:23,050 And so then you have to figure out how to write that. 676 00:34:23,050 --> 00:34:30,340 And so you would have three ones down in energy, minus 2/5 times 677 00:34:30,340 --> 00:34:34,030 the octahedral crystal field splitting energy. 678 00:34:34,030 --> 00:34:40,270 And you would have one electron, up by 3/5 times 679 00:34:40,270 --> 00:34:44,080 the octahedral crystal field splitting energy. 680 00:34:44,080 --> 00:34:50,710 So minus 6 plus 3 is minus 3/5 times the octahedral crystal 681 00:34:50,710 --> 00:34:52,480 field splitting energy. 682 00:34:52,480 --> 00:34:56,350 So this problem required you to know what high spin was, 683 00:34:56,350 --> 00:35:00,490 then correctly identify the weak field diagram, 684 00:35:00,490 --> 00:35:04,420 and then figure out the crystal field stabilization energy. 685 00:35:04,420 --> 00:35:06,820 So that was actually quite good. 686 00:35:06,820 --> 00:35:12,250 And maybe you'll remember the high spin, low spin definitions 687 00:35:12,250 --> 00:35:13,630 as well. 688 00:35:13,630 --> 00:35:23,140 OK, so let's just do one more thing and then 689 00:35:23,140 --> 00:35:27,010 we'll-- because we've just been talking about high spin. 690 00:35:27,010 --> 00:35:31,180 So back to our compounds, we're going to talk about magnetism. 691 00:35:31,180 --> 00:35:33,910 And then we're going to come back next time 692 00:35:33,910 --> 00:35:34,840 and talk about color. 693 00:35:34,840 --> 00:35:38,240 And we have some cool demos for color which we'll do next time. 694 00:35:38,240 --> 00:35:41,440 But before we leave from this, our iron compounds, 695 00:35:41,440 --> 00:35:44,470 we want to think about whether they're paramagnetic, which is 696 00:35:44,470 --> 00:35:45,970 attracted by a magnetic field. 697 00:35:45,970 --> 00:35:48,330 Or diamagnetic, repelled by a magnetic field. 698 00:35:48,330 --> 00:35:50,740 And we've already talked about this in this class. 699 00:35:50,740 --> 00:35:54,310 So, based-- and here are our iron diagrams again. 700 00:35:54,310 --> 00:35:56,200 Based on these diagrams, would you 701 00:35:56,200 --> 00:36:00,770 expect these to be paramagnetic, or diamagnetic? 702 00:36:00,770 --> 00:36:01,860 Paramedic. 703 00:36:01,860 --> 00:36:05,550 And that was because it has what kind of electrons? 704 00:36:05,550 --> 00:36:06,700 Paired, right. 705 00:36:06,700 --> 00:36:09,370 So here you just have to remember your definition 706 00:36:09,370 --> 00:36:10,860 of paramagnetic. 707 00:36:10,860 --> 00:36:12,760 It has unpaired electrons. 708 00:36:12,760 --> 00:36:16,390 Now, normally, things with a weak field, and a high spin, 709 00:36:16,390 --> 00:36:18,610 are going to be more likely to be paramagnetic, 710 00:36:18,610 --> 00:36:20,530 have unpaired electrons. 711 00:36:20,530 --> 00:36:23,500 Things that have a very strong field. 712 00:36:23,500 --> 00:36:26,230 And so you pair first, before you fill up. 713 00:36:26,230 --> 00:36:28,570 Minimum number-- low spin, minimum number 714 00:36:28,570 --> 00:36:32,050 of unpaired electrons are more likely to be diamagnetic. 715 00:36:32,050 --> 00:36:34,240 But in this case, we didn't have enough electrons, 716 00:36:34,240 --> 00:36:36,849 so they're still both paramagnetic. 717 00:36:36,849 --> 00:36:38,140 All right, so we'll stop there. 718 00:36:38,140 --> 00:36:41,620 We'll come back and talk about the colors of those iron 719 00:36:41,620 --> 00:36:42,700 compounds. 720 00:36:42,700 --> 00:36:45,850 And more colors and cool demos on Friday. 721 00:36:45,850 --> 00:36:46,660 Don't miss Friday. 722 00:36:46,660 --> 00:36:50,290 Remember, Friday, double clicker competition. 723 00:36:50,290 --> 00:36:54,820 The team that comes in second is automatically in the playoffs. 724 00:37:02,070 --> 00:37:02,653 Are you-- 725 00:37:02,653 --> 00:37:04,990 AUDIENCE: We're at 166, but it stopped. 726 00:37:04,990 --> 00:37:07,290 PROFESSOR: OK, let's just take 10 more a seconds 727 00:37:07,290 --> 00:37:08,700 on the clicker question. 728 00:37:22,900 --> 00:37:25,812 All right, let's quiet down. 729 00:37:28,410 --> 00:37:31,440 I'd like to see the 85% that's good. 730 00:37:31,440 --> 00:37:34,140 Of course it doesn't distinguish all that much for the clicker 731 00:37:34,140 --> 00:37:35,060 competition today. 732 00:37:37,830 --> 00:37:40,190 So if we can quiet down a little bit. 733 00:37:43,890 --> 00:37:46,710 People can just yell out. 734 00:37:46,710 --> 00:37:49,410 What would this have been the correct answer to? 735 00:37:49,410 --> 00:37:51,390 What should the question have said for that 736 00:37:51,390 --> 00:37:53,840 to be the correct answer? 737 00:37:53,840 --> 00:37:55,290 Low spin, right. 738 00:37:55,290 --> 00:37:59,520 So low spin-- shh-- is the minimum number 739 00:37:59,520 --> 00:38:01,900 of unpaired electrons. 740 00:38:01,900 --> 00:38:04,320 And so this is the low spin. 741 00:38:04,320 --> 00:38:07,900 High spin is the maximum number of unpaired electrons. 742 00:38:07,900 --> 00:38:09,930 So this is the correct diagram. 743 00:38:09,930 --> 00:38:12,820 And C is wrong. 744 00:38:12,820 --> 00:38:15,570 It's not correct for either high or low spin. 745 00:38:15,570 --> 00:38:18,600 Because we have two electrons here 746 00:38:18,600 --> 00:38:20,430 that would have the same four quantum 747 00:38:20,430 --> 00:38:22,710 numbers, which is not allowed. 748 00:38:22,710 --> 00:38:27,070 OK, so let's continue on with the lecture. 749 00:38:27,070 --> 00:38:30,330 And we are talking about colors. 750 00:38:30,330 --> 00:38:32,370 So, we're talking-- we're talking 751 00:38:32,370 --> 00:38:34,740 about the colors of the two iron compounds 752 00:38:34,740 --> 00:38:36,630 that we had described before. 753 00:38:36,630 --> 00:38:38,010 And so let's continue. 754 00:38:38,010 --> 00:38:41,460 And when we talk about colors, we need to do a little review 755 00:38:41,460 --> 00:38:45,210 and think about what's happening when a substance gives off 756 00:38:45,210 --> 00:38:47,370 a color. 757 00:38:47,370 --> 00:38:50,340 And so, when a substance-- whether a substance is going 758 00:38:50,340 --> 00:38:54,750 to absorb a photon or not, to excite an electron to a higher 759 00:38:54,750 --> 00:38:57,180 energy level that then, when it falls back, 760 00:38:57,180 --> 00:38:59,314 will emit a beautiful light. 761 00:38:59,314 --> 00:39:01,230 We can talk about whether a substance is going 762 00:39:01,230 --> 00:39:02,790 to absorb a photon or not. 763 00:39:02,790 --> 00:39:06,600 And it will if the energy of that photon 764 00:39:06,600 --> 00:39:09,850 is equal to the difference in that energy level. 765 00:39:09,850 --> 00:39:11,470 So we talked about this before. 766 00:39:11,470 --> 00:39:14,700 Exam one, exam two, somewhere around there. 767 00:39:14,700 --> 00:39:17,820 And so, we saw this equation a lot. 768 00:39:17,820 --> 00:39:20,760 That the energy equals Planck's constant, times the frequency 769 00:39:20,760 --> 00:39:21,780 of the light. 770 00:39:21,780 --> 00:39:24,750 And now we can take that same gorgeous equation 771 00:39:24,750 --> 00:39:26,610 and add a little thing to it. 772 00:39:26,610 --> 00:39:28,320 So we can add that that energy is 773 00:39:28,320 --> 00:39:32,130 going to be equal to the octahedral crystal field 774 00:39:32,130 --> 00:39:34,240 splitting energy. 775 00:39:34,240 --> 00:39:37,380 And so, a substance, one of these transition metal 776 00:39:37,380 --> 00:39:41,010 complexes, will absorb a photon of light 777 00:39:41,010 --> 00:39:44,550 if the energy of that photon is equal to this splitting 778 00:39:44,550 --> 00:39:45,510 difference. 779 00:39:45,510 --> 00:39:49,800 And if it is, it can promote an electron between a lower 780 00:39:49,800 --> 00:39:51,630 and a higher state. 781 00:39:51,630 --> 00:39:53,192 So this is all the same kind of thing 782 00:39:53,192 --> 00:39:55,650 that we talked about before, but now we're just applying it 783 00:39:55,650 --> 00:39:58,020 to transition metals. 784 00:39:58,020 --> 00:40:01,770 So, let's think about what's happening with our iron 785 00:40:01,770 --> 00:40:03,150 complex. 786 00:40:03,150 --> 00:40:06,270 And if we say, had a low frequency 787 00:40:06,270 --> 00:40:08,550 of light that was absorbed, what would 788 00:40:08,550 --> 00:40:10,080 be true about the wavelength? 789 00:40:10,080 --> 00:40:12,420 Would it be long or short? 790 00:40:12,420 --> 00:40:13,500 It would be long. 791 00:40:13,500 --> 00:40:15,880 And how do we know this? 792 00:40:15,880 --> 00:40:19,820 We know this from the fact that if you're talking about light, 793 00:40:19,820 --> 00:40:23,650 the speed of light equals the wavelength times the frequency. 794 00:40:23,650 --> 00:40:26,100 So if you have a low frequency, then you're 795 00:40:26,100 --> 00:40:28,610 going to have a long wavelength. 796 00:40:28,610 --> 00:40:32,190 So our long wavelengths, then, are on this 797 00:40:32,190 --> 00:40:36,600 and over here, sort of our yellow, orange, red, with red 798 00:40:36,600 --> 00:40:39,670 being our longest wavelength. 799 00:40:39,670 --> 00:40:42,960 So if, then, we have a high frequency of light absorbed, 800 00:40:42,960 --> 00:40:45,240 then the wavelength would be short. 801 00:40:45,240 --> 00:40:47,280 So it'll be short wavelength absorbed. 802 00:40:47,280 --> 00:40:49,020 And so, again, our short wavelengths 803 00:40:49,020 --> 00:40:52,820 are down here, with our shortest being the violet wavelength. 804 00:40:52,820 --> 00:40:56,910 All right, and now, the color that you actually see 805 00:40:56,910 --> 00:41:01,020 is the one that is complimentary to the color that 806 00:41:01,020 --> 00:41:03,270 is of the absorbed light. 807 00:41:03,270 --> 00:41:07,170 So we're going to think about how big those energy 808 00:41:07,170 --> 00:41:09,420 differences are, whether that translates 809 00:41:09,420 --> 00:41:12,720 to high frequency, low frequency, long wavelength, 810 00:41:12,720 --> 00:41:15,660 short length-- wavelength for the absorb light. 811 00:41:15,660 --> 00:41:18,570 And then, the complimentary of the absorb light 812 00:41:18,570 --> 00:41:21,810 is the light that we see, the transmitted light. 813 00:41:21,810 --> 00:41:24,180 All right, so let's think about the iron complexes 814 00:41:24,180 --> 00:41:26,040 that we talked about. 815 00:41:26,040 --> 00:41:30,330 And we had a high spin, or a higher spin, iron water 816 00:41:30,330 --> 00:41:30,920 complex. 817 00:41:30,920 --> 00:41:36,650 Water is actually kind of an intermediate field ligand. 818 00:41:36,650 --> 00:41:41,760 And it absorbs low frequency, or a longer wavelength of light. 819 00:41:41,760 --> 00:41:45,230 And so it's going to transmit on the shorter end of things. 820 00:41:45,230 --> 00:41:48,140 Again, water sort of an intermediate field. 821 00:41:48,140 --> 00:41:53,340 But in this case, it was less strong than our other one, 822 00:41:53,340 --> 00:41:55,410 which was cyanide, which is very strong. 823 00:41:55,410 --> 00:41:58,330 And, actually, these iron water complexes 824 00:41:58,330 --> 00:42:00,311 can appear actually a variety of colors. 825 00:42:00,311 --> 00:42:02,435 If they're solid, they're more of this pale violet. 826 00:42:02,435 --> 00:42:05,960 So definitely a very short color wavelength that we're seeing. 827 00:42:05,960 --> 00:42:07,940 But in solution, and depending on the pH, 828 00:42:07,940 --> 00:42:11,540 they can be sort of yellowish, brownish color. 829 00:42:11,540 --> 00:42:14,460 But the strong field ligand, remember the other compound 830 00:42:14,460 --> 00:42:15,580 had cyanide on it. 831 00:42:15,580 --> 00:42:17,810 That's a very strong field ligand. 832 00:42:17,810 --> 00:42:20,920 And so that's going to absorb, then, a high frequency. 833 00:42:20,920 --> 00:42:23,720 So a strong field, so you have a big energy difference. 834 00:42:23,720 --> 00:42:26,710 So you have a big energy, high frequency, and therefore short 835 00:42:26,710 --> 00:42:27,560 wavelength. 836 00:42:27,560 --> 00:42:32,100 So it will transmit on the longer end of things. 837 00:42:32,100 --> 00:42:35,810 And this is actually a bright orange red color. 838 00:42:35,810 --> 00:42:39,650 So you have a very long, long wavelength 839 00:42:39,650 --> 00:42:41,020 that you're observing here. 840 00:42:41,020 --> 00:42:42,860 This beautiful red orange. 841 00:42:42,860 --> 00:42:44,390 It's a really brilliant color. 842 00:42:44,390 --> 00:42:47,730 Now interestingly, I mentioned in terms of applications, 843 00:42:47,730 --> 00:42:50,690 as some transition metal complexes were used to color 844 00:42:50,690 --> 00:42:53,630 things-- and I mentioned the blue in blueprint-- 845 00:42:53,630 --> 00:42:57,350 and if you take this compound and actually add iron 846 00:42:57,350 --> 00:42:59,330 in a different oxidation state to it, 847 00:42:59,330 --> 00:43:02,600 and, form this complex that has iron plus 3, 848 00:43:02,600 --> 00:43:05,390 and iron plus true with cyanide, you actually 849 00:43:05,390 --> 00:43:07,160 get the blueprint blue. 850 00:43:07,160 --> 00:43:10,000 So the colors can be just dramatically different 851 00:43:10,000 --> 00:43:14,120 depending on what gets added to the system. 852 00:43:14,120 --> 00:43:17,160 All right, so now let's think about-- it's a little sad-- 853 00:43:17,160 --> 00:43:19,210 but things without color. 854 00:43:19,210 --> 00:43:23,230 So what coordination complexes would be colorless? 855 00:43:23,230 --> 00:43:26,910 What would be true about the d orbitals 856 00:43:26,910 --> 00:43:29,960 If you had a colorless thing? 857 00:43:29,960 --> 00:43:31,743 Yeah, what would be true? 858 00:43:31,743 --> 00:43:33,774 AUDIENCE: [INAUDIBLE] 859 00:43:33,774 --> 00:43:35,690 PROFESSOR: Yeah, they could all be degenerate, 860 00:43:35,690 --> 00:43:37,979 so there's no splitting at all. 861 00:43:37,979 --> 00:43:40,520 Which usually doesn't happen if there are any ligands around. 862 00:43:40,520 --> 00:43:43,040 That's their hypothetical spherical crystal field, 863 00:43:43,040 --> 00:43:44,290 which I brought with me again. 864 00:43:44,290 --> 00:43:45,664 Because I just love carrying this 865 00:43:45,664 --> 00:43:49,250 through the infinite corridor and have people look at me. 866 00:43:49,250 --> 00:43:52,400 But, if you do have the ligands around, it will happen. 867 00:43:52,400 --> 00:43:54,830 If all of your d orbitals are filled, 868 00:43:54,830 --> 00:43:57,140 or if the energy levels are basically 869 00:43:57,140 --> 00:43:58,940 out of the visible range. 870 00:43:58,940 --> 00:44:01,910 So the transitions are not in the visible range at all. 871 00:44:01,910 --> 00:44:04,000 So, if they're all filled-- so, there's 872 00:44:04,000 --> 00:44:07,580 no way that you can move an electron. 873 00:44:07,580 --> 00:44:09,020 Or, if you can. 874 00:44:09,020 --> 00:44:12,250 But it's outside the visible region 875 00:44:12,250 --> 00:44:14,690 All right, so now let's think about some examples 876 00:44:14,690 --> 00:44:18,710 of what transition metals would fit into this. 877 00:44:18,710 --> 00:44:20,459 And I'll bring up my periodic table. 878 00:44:20,459 --> 00:44:22,250 And we'll also bring up a clicker question. 879 00:44:33,230 --> 00:44:36,530 All right, let's just take 10 more seconds on this. 880 00:44:51,900 --> 00:44:53,230 All right. 881 00:44:53,230 --> 00:44:55,144 So we can take a look at this. 882 00:44:58,640 --> 00:45:03,220 And with our periodic table, we have nickel and palladium, 883 00:45:03,220 --> 00:45:06,350 group 10 minus 2 is 8. 884 00:45:06,350 --> 00:45:11,020 Copper plus 2, gold plus 2, 11 minus 2 is 9. 885 00:45:11,020 --> 00:45:15,560 Zinc plus 2, cadmium plus 2, twelve minus 2 is 10. 886 00:45:15,560 --> 00:45:18,770 And so 10 would be the correct number for our field d 887 00:45:18,770 --> 00:45:19,310 orbitals. 888 00:45:19,310 --> 00:45:23,310 They can hold 10 electrons. 889 00:45:23,310 --> 00:45:27,920 S if we, then, go and fill this in, examples would include: 890 00:45:27,920 --> 00:45:32,830 zinc plus 2, and cadmium plus 2, with our d10 system. 891 00:45:32,830 --> 00:45:38,560 And in fact, zinc plus 2 is a very common oxidation state 892 00:45:38,560 --> 00:45:39,560 for zinc. 893 00:45:39,560 --> 00:45:41,630 Many proteins require zinc. 894 00:45:41,630 --> 00:45:44,120 Many of you have zinc in vitamin tablets. 895 00:45:44,120 --> 00:45:46,460 Some people take extra zinc to make 896 00:45:46,460 --> 00:45:49,690 sure you have enough zinc plus 2 in your body. 897 00:45:49,690 --> 00:45:52,820 And a lot of times people who are studying proteins 898 00:45:52,820 --> 00:45:55,790 do not realize it's a zinc containing protein because they 899 00:45:55,790 --> 00:45:57,147 isolate the protein. 900 00:45:57,147 --> 00:45:58,730 And it's clear, so they don't think it 901 00:45:58,730 --> 00:46:00,370 has a transition metal in it. 902 00:46:00,370 --> 00:46:02,290 But zinc is hiding in that protein 903 00:46:02,290 --> 00:46:04,850 because it's colorless so you don't know it's there. 904 00:46:04,850 --> 00:46:08,330 If you purify a protein with color with other metals, 905 00:46:08,330 --> 00:46:10,400 it's really obvious that the metal is there. 906 00:46:10,400 --> 00:46:13,040 But zinc can be sneaky. 907 00:46:13,040 --> 00:46:14,810 Cadmium can also be sneaky. 908 00:46:14,810 --> 00:46:18,110 Cadmium, for the most part, is a poison to us. 909 00:46:18,110 --> 00:46:21,590 And they used to use it to coat barbecue grills. 910 00:46:21,590 --> 00:46:23,090 Which is not-- you don't want to put 911 00:46:23,090 --> 00:46:25,830 a poisonous substance on a barbecue grill 912 00:46:25,830 --> 00:46:26,710 and then heat it up. 913 00:46:26,710 --> 00:46:28,870 That's a really bad idea. 914 00:46:28,870 --> 00:46:31,270 So if you go to a barbecue and you think, 915 00:46:31,270 --> 00:46:35,362 wow, that grill looks like it's, like, 70 or 80 years old, 916 00:46:35,362 --> 00:46:36,320 or something like that. 917 00:46:36,320 --> 00:46:37,460 It looks ancient. 918 00:46:37,460 --> 00:46:40,190 Maybe you don't want to eat from that barbecue grill. 919 00:46:40,190 --> 00:46:42,790 They don't do this anymore, but old barbecue grills 920 00:46:42,790 --> 00:46:43,960 had cadmium on it. 921 00:46:43,960 --> 00:46:47,390 And I know someone who actually had cadmium poisoning. 922 00:46:47,390 --> 00:46:49,730 And it was a really pretty terrible thing because it's 923 00:46:49,730 --> 00:46:50,980 hard to diagnose that. 924 00:46:50,980 --> 00:46:53,270 But they finally got the right diagnosis. 925 00:46:53,270 --> 00:46:55,400 All right, so again, colorless things, 926 00:46:55,400 --> 00:46:58,610 you don't know that they're there, but they sometimes are. 927 00:46:58,610 --> 00:47:01,376 All right, so what about cobalt plus 3? 928 00:47:01,376 --> 00:47:02,500 You can just yell this out. 929 00:47:02,500 --> 00:47:06,910 Would this be a colorless compound? 930 00:47:06,910 --> 00:47:07,750 No. 931 00:47:07,750 --> 00:47:13,550 So we have in our group 9, minus 3 would be sync -- would be 6. 932 00:47:13,550 --> 00:47:14,770 So it's not. 933 00:47:14,770 --> 00:47:17,390 Which vitamin contains cobalt? 934 00:47:17,390 --> 00:47:19,030 And you probably all know because we've 935 00:47:19,030 --> 00:47:20,350 been talking about it. 936 00:47:20,350 --> 00:47:22,030 Vitamin B-12. 937 00:47:22,030 --> 00:47:24,490 And I just thought I would share with you 938 00:47:24,490 --> 00:47:27,790 the colors of vitamin B-12. 939 00:47:27,790 --> 00:47:31,720 And so this is crystals that contain vitamin B-12. 940 00:47:31,720 --> 00:47:34,570 And these are their actual colors of the crystals. 941 00:47:34,570 --> 00:47:37,210 So it's really fun to work with vitamin B12. 942 00:47:37,210 --> 00:47:39,160 It's absolutely brilliant. 943 00:47:39,160 --> 00:47:41,030 Except that it's also light sensitive. 944 00:47:41,030 --> 00:47:43,660 So you have to work in the dark, under red light. 945 00:47:43,660 --> 00:47:46,420 So everything, then, is red because you're under red light. 946 00:47:46,420 --> 00:47:48,910 But if you bring them out, and you expose them to light, 947 00:47:48,910 --> 00:47:50,320 they're really, really pretty. 948 00:47:50,320 --> 00:47:52,778 All right, so we're going to continue on this cobalt theme. 949 00:47:52,778 --> 00:47:56,080 Because cobalt is one of the most spectacular transition 950 00:47:56,080 --> 00:47:58,160 metals when it comes to color. 951 00:47:58,160 --> 00:48:01,156 And I'm going to get you ready for a little demo. 952 00:48:01,156 --> 00:48:02,530 And you're going to help me first 953 00:48:02,530 --> 00:48:05,770 figure out what colors you should observe in this demo. 954 00:48:05,770 --> 00:48:10,640 All right, so, we're going to have a cobalt compound that 955 00:48:10,640 --> 00:48:12,940 has six waters with it. 956 00:48:12,940 --> 00:48:17,780 And you're given the octahedral crystal field splitting energy. 957 00:48:17,780 --> 00:48:19,840 So now we want to predict the color. 958 00:48:19,840 --> 00:48:21,790 And when we predict the color, we're 959 00:48:21,790 --> 00:48:23,740 asking about what sort of wavelength 960 00:48:23,740 --> 00:48:24,750 is going to be absorbed. 961 00:48:24,750 --> 00:48:26,249 So we can think about the wavelength 962 00:48:26,249 --> 00:48:27,410 that will be transmitted. 963 00:48:27,410 --> 00:48:29,830 So we need to think about our equations. 964 00:48:29,830 --> 00:48:33,250 And we can combine these just like we did in many problems 965 00:48:33,250 --> 00:48:35,110 in the earlier part of the course. 966 00:48:35,110 --> 00:48:37,930 And so wavelength equals Planck's constant times 967 00:48:37,930 --> 00:48:38,950 the speed of light. 968 00:48:38,950 --> 00:48:41,200 Now, instead of just divided by any energy, 969 00:48:41,200 --> 00:48:44,050 we're dividing by the energy that's the octahedral crystal 970 00:48:44,050 --> 00:48:46,130 field splitting energy. 971 00:48:46,130 --> 00:48:48,010 And so we can put in our Planck's constant 972 00:48:48,010 --> 00:48:49,430 and our speed of light. 973 00:48:49,430 --> 00:48:52,360 And we can put in the octahedral crystal field splitting energy 974 00:48:52,360 --> 00:48:53,560 that we were given. 975 00:48:53,560 --> 00:48:57,250 But we want units in meters. 976 00:48:57,250 --> 00:49:00,920 And so we need our joules to cancel out. 977 00:49:00,920 --> 00:49:03,220 And in the bottom we're given the splitting energy 978 00:49:03,220 --> 00:49:04,220 in kilojoules. 979 00:49:04,220 --> 00:49:06,220 So we need to do some conversions. 980 00:49:06,220 --> 00:49:08,450 So first we need to get rid of this kilojoules. 981 00:49:08,450 --> 00:49:10,540 So we're going to convert it to joules. 982 00:49:10,540 --> 00:49:13,330 Then we can get rid of our joules. 983 00:49:13,330 --> 00:49:14,440 We also have seconds. 984 00:49:14,440 --> 00:49:16,420 We don't want seconds in our wavelength. 985 00:49:16,420 --> 00:49:19,790 But that is going to cancel out here and here, so we're good. 986 00:49:19,790 --> 00:49:22,550 But now our answer, we have meters at the top, 987 00:49:22,550 --> 00:49:24,550 but we have moles on the bottom. 988 00:49:24,550 --> 00:49:27,917 So we need to use Avogadro's number to cancel out our moles. 989 00:49:27,917 --> 00:49:29,500 And if you don't do that, you're going 990 00:49:29,500 --> 00:49:33,190 to get a really weird number for your wavelength that's 991 00:49:33,190 --> 00:49:34,380 not going to make sense. 992 00:49:34,380 --> 00:49:35,796 It's going to be off by something, 993 00:49:35,796 --> 00:49:38,320 like, a factor of 10 to the 23. 994 00:49:38,320 --> 00:49:41,410 That should remind you, you want to use Avogadro's number here 995 00:49:41,410 --> 00:49:43,540 to get rid of your per mole. 996 00:49:43,540 --> 00:49:47,230 All right, so now we have a wavelength. 997 00:49:47,230 --> 00:49:50,470 And yes, on your equation sheet, we will give you this. 998 00:49:50,470 --> 00:49:52,270 We will give you the color spectrums. 999 00:49:52,270 --> 00:49:54,410 You don't have to memorize this. 1000 00:49:54,410 --> 00:49:59,500 So about 500 nanometers is in our green region over here. 1001 00:49:59,500 --> 00:50:02,530 So the color that should be absorbed, 1002 00:50:02,530 --> 00:50:06,680 given this octahedral crystal field splitting energy, 1003 00:50:06,680 --> 00:50:07,990 is green. 1004 00:50:07,990 --> 00:50:15,740 So now, for green, what is the complementary color of green? 1005 00:50:15,740 --> 00:50:17,690 Yup, so it's going to be reddish. 1006 00:50:17,690 --> 00:50:19,780 We have our little drawing over here. 1007 00:50:19,780 --> 00:50:22,940 So the predicted color would be red. 1008 00:50:22,940 --> 00:50:25,742 So let me just now tell you about this demo. 1009 00:50:25,742 --> 00:50:27,700 And we're actually going to see some red color. 1010 00:50:27,700 --> 00:50:31,400 But we're also going to see another color which is blue. 1011 00:50:31,400 --> 00:50:37,000 So, in this demo, if you have, start with some copper chloride 1012 00:50:37,000 --> 00:50:38,500 and add a lot of water. 1013 00:50:38,500 --> 00:50:39,460 A lot, a lot of water. 1014 00:50:39,460 --> 00:50:40,870 Hydrate it really well. 1015 00:50:40,870 --> 00:50:44,290 You'll get this octahedral system 1016 00:50:44,290 --> 00:50:46,330 that you just told me was red. 1017 00:50:46,330 --> 00:50:48,310 But if you don't add a lot of water, 1018 00:50:48,310 --> 00:50:49,780 just a little bit of water, you'll 1019 00:50:49,780 --> 00:50:52,270 only display some of the chlorides. 1020 00:50:52,270 --> 00:50:54,560 And then you're going to have a blue system. 1021 00:50:54,560 --> 00:50:56,950 So if you have a lot of water, red. 1022 00:50:56,950 --> 00:50:58,840 And you're hydrated, red. 1023 00:50:58,840 --> 00:51:01,490 If you're more dehydrated, you get blue. 1024 00:51:01,490 --> 00:51:04,680 So we're going to now try this out and see if it works. 1025 00:51:10,190 --> 00:51:11,190 GUEST SPEAKER: Is it on? 1026 00:51:11,190 --> 00:51:11,773 Yeah, it's on. 1027 00:51:11,773 --> 00:51:12,600 Great. 1028 00:51:12,600 --> 00:51:15,426 OK, so that's the cobalt flower. 1029 00:51:15,426 --> 00:51:17,800 And as Cathy said, it's-- oh, we're going to put it under 1030 00:51:17,800 --> 00:51:18,850 there. 1031 00:51:18,850 --> 00:51:23,230 As Cathy said, it's got some cobalt. 1032 00:51:23,230 --> 00:51:25,376 And it's got water ligands. 1033 00:51:25,376 --> 00:51:26,500 And it's also got chlorine. 1034 00:51:26,500 --> 00:51:29,034 And Eric's going to sprinkle it with water now. 1035 00:51:29,034 --> 00:51:30,700 PROFESSOR: So we're going to hydrate it. 1036 00:51:30,700 --> 00:51:32,740 GUEST SPEAKER: Hydrate it, as you do, 1037 00:51:32,740 --> 00:51:34,210 when you have to water a flower. 1038 00:51:34,210 --> 00:51:40,680 And it's turned, like, it's a pinkish, reddish color, right? 1039 00:51:40,680 --> 00:51:42,220 Can they see that up there? 1040 00:51:42,220 --> 00:51:42,760 Yeah. 1041 00:51:42,760 --> 00:51:44,218 PROFESSOR: It looks better with it. 1042 00:51:44,218 --> 00:51:45,800 Hold it against this, too, I think. 1043 00:51:45,800 --> 00:51:46,675 GUEST SPEAKER: Right. 1044 00:51:49,060 --> 00:51:52,720 So to show you that it was, in fact, the water 1045 00:51:52,720 --> 00:51:56,390 that led to this color change, we're 1046 00:51:56,390 --> 00:52:01,460 going to try to dry out the flower. 1047 00:52:01,460 --> 00:52:02,550 Is it working? 1048 00:52:02,550 --> 00:52:03,190 Am I on hot? 1049 00:52:03,190 --> 00:52:04,231 Yes, I am. 1050 00:52:04,231 --> 00:52:05,230 I know it's really slow. 1051 00:52:05,230 --> 00:52:06,438 I'd just rather it go faster. 1052 00:52:09,530 --> 00:52:12,930 And, well-- 1053 00:52:12,930 --> 00:52:14,621 PROFESSOR: Yeah. 1054 00:52:14,621 --> 00:52:16,620 Why don't you hold it under the document camera? 1055 00:52:16,620 --> 00:52:18,520 I think you can kind of see it happening. 1056 00:52:27,050 --> 00:52:29,610 GUEST SPEAKER: So as-- there we go. 1057 00:52:29,610 --> 00:52:30,360 That's working. 1058 00:52:30,360 --> 00:52:32,760 As Eric continues to warm this thing up, 1059 00:52:32,760 --> 00:52:35,070 the water is evaporating. 1060 00:52:35,070 --> 00:52:39,150 And as that happens, it starts forming that hydrous chloride 1061 00:52:39,150 --> 00:52:41,190 complex instead of up here, hydrous complex, 1062 00:52:41,190 --> 00:52:45,420 and it's going back to emitting blue color instead of red. 1063 00:52:45,420 --> 00:52:49,200 And hopefully we can see. 1064 00:52:49,200 --> 00:52:50,060 Oh, there. 1065 00:52:50,060 --> 00:52:50,773 It's working. 1066 00:52:50,773 --> 00:52:52,560 Yea. 1067 00:52:52,560 --> 00:52:54,890 PROFESSOR: So some people give each other roses. 1068 00:52:54,890 --> 00:52:59,100 But if your significant other is a geek, what's 1069 00:52:59,100 --> 00:53:02,410 better than a flower that changes color on hydration? 1070 00:53:02,410 --> 00:53:03,130 I don't know. 1071 00:53:03,130 --> 00:53:05,940 I think this is a pretty good gift. 1072 00:53:05,940 --> 00:53:07,890 Valentine's Day isn't quite coming up, 1073 00:53:07,890 --> 00:53:08,990 but just keep it in mind. 1074 00:53:11,630 --> 00:53:14,760 All right, so we'll leave the flower here 1075 00:53:14,760 --> 00:53:19,560 and we'll keep an eye on it as we go along. 1076 00:53:19,560 --> 00:53:21,460 It will change back eventually. 1077 00:53:21,460 --> 00:53:24,060 It depends a lot on the weather, but it's pretty dry right now 1078 00:53:24,060 --> 00:53:26,220 in this time of year.