1 00:00:00,030 --> 00:00:02,400 The following content is provided under a Creative 2 00:00:02,400 --> 00:00:03,840 Commons license. 3 00:00:03,840 --> 00:00:06,850 Your support will help MIT OpenCourseWare continue to 4 00:00:06,850 --> 00:00:10,520 offer high-quality educational resources for free. 5 00:00:10,520 --> 00:00:13,390 To make a donation or view additional materials from 6 00:00:13,390 --> 00:00:17,490 hundreds of MIT courses, visit MIT OpenCourseWare at 7 00:00:17,490 --> 00:00:18,740 ocw.mit.edu. 8 00:00:21,020 --> 00:00:22,880 Tuesday will be the first weekly quiz, 9 00:00:22,880 --> 00:00:25,170 celebration that is. 10 00:00:25,170 --> 00:00:26,790 That will be at the beginning of recitation. 11 00:00:26,790 --> 00:00:28,620 You'll have 10 minutes. 12 00:00:28,620 --> 00:00:31,270 It'll be a short one-pager. 13 00:00:31,270 --> 00:00:33,170 You just write on the page. 14 00:00:33,170 --> 00:00:36,560 All you bring is your periodic table, which you should have 15 00:00:36,560 --> 00:00:38,250 gotten in recitation yesterday. 16 00:00:38,250 --> 00:00:42,190 Periodic Table, table of constants, calculator, 17 00:00:42,190 --> 00:00:47,000 something to write with, but no aid sheet on the weeklies. 18 00:00:47,000 --> 00:00:49,910 Readings: Readings, I urge you to read 19 00:00:49,910 --> 00:00:51,720 before you come to class. 20 00:00:51,720 --> 00:00:54,680 And so if you go to the website, you can go to 21 00:00:54,680 --> 00:00:57,560 Schedule, and in the schedule, you'll see stuff like this 22 00:00:57,560 --> 00:01:01,860 that tells you what the readings are for the day. 23 00:01:01,860 --> 00:01:04,640 As I mentioned last day, the lectures are being 24 00:01:04,640 --> 00:01:09,990 videographed and posted probably within an hour on the 25 00:01:09,990 --> 00:01:15,630 website and any of the images that I show are also recorded, 26 00:01:15,630 --> 00:01:18,150 burned as PDFs and uploaded. 27 00:01:18,150 --> 00:01:23,640 So you don't have to be put in high-speed stenographic mode 28 00:01:23,640 --> 00:01:27,160 in order to attend class. 29 00:01:27,160 --> 00:01:29,260 What's the other thing I wanted to tell you? 30 00:01:29,260 --> 00:01:32,340 If you're new to the class or if you need to change your 31 00:01:32,340 --> 00:01:36,820 recitation section because your conditions have changed, 32 00:01:36,820 --> 00:01:39,780 do not simply go to the other class. 33 00:01:39,780 --> 00:01:41,350 We're trying to regulate enrollment, 34 00:01:41,350 --> 00:01:42,680 particularly on Tuesdays. 35 00:01:42,680 --> 00:01:46,740 If the TA shows up expecting 20 students and has 20 copies 36 00:01:46,740 --> 00:01:49,950 of the quiz and 25 people show up, that's not 37 00:01:49,950 --> 00:01:51,240 a recipe for success. 38 00:01:51,240 --> 00:01:54,510 So you must go to my administrative assistant, 39 00:01:54,510 --> 00:01:57,300 Hilary Sheldon in order to change recitation. 40 00:01:57,300 --> 00:01:59,830 And if you need any of the handouts and so on, it's just 41 00:01:59,830 --> 00:02:04,740 down the hall here in Building 8, Room 201. 42 00:02:04,740 --> 00:02:06,720 I think that's all that I had to say. 43 00:02:06,720 --> 00:02:09,160 If you go here the videos are all listed. 44 00:02:09,160 --> 00:02:14,040 So last day we started talking about taxonomy and that led us 45 00:02:14,040 --> 00:02:16,270 to the beginnings of atomic theory. 46 00:02:16,270 --> 00:02:19,790 We visited with Democritus, 400 BC. 47 00:02:19,790 --> 00:02:22,790 We had that detour with the idiocy of Aristotle, and then 48 00:02:22,790 --> 00:02:26,510 eventually got back to our senses, and we saw John Dalton 49 00:02:26,510 --> 00:02:30,540 with his table of the elements, and then ultimately 50 00:02:30,540 --> 00:02:32,260 onto Mendeleyev. 51 00:02:32,260 --> 00:02:35,240 And I wanted to pick up the thread there. 52 00:02:35,240 --> 00:02:38,390 But before doing so, draw attention the fact that John 53 00:02:38,390 --> 00:02:42,900 Dalton did more than simply develop a set of fonts for us. 54 00:02:42,900 --> 00:02:46,090 So he proposed the model of the atom and this goes back 55 00:02:46,090 --> 00:02:50,440 little over 200 years ago, and these are the 56 00:02:50,440 --> 00:02:52,120 features of the model. 57 00:02:52,120 --> 00:02:54,680 First of all, that matter is composed of atoms that are 58 00:02:54,680 --> 00:02:56,360 indivisible and indestructible. 59 00:02:56,360 --> 00:02:57,560 So that goes all the way back to 60 00:02:57,560 --> 00:03:00,780 Democritus, nothing new there. 61 00:03:00,780 --> 00:03:02,685 All atoms of an element are identical. 62 00:03:05,240 --> 00:03:08,330 Atoms of different elements have different weights and 63 00:03:08,330 --> 00:03:09,550 different chemical properties. 64 00:03:09,550 --> 00:03:12,170 This is the emergence of modern material science, the 65 00:03:12,170 --> 00:03:15,410 connection between properties and elements. 66 00:03:15,410 --> 00:03:18,900 So the weight arguably is one of the properties, but the 67 00:03:18,900 --> 00:03:20,910 only way they could distinguish elements at that 68 00:03:20,910 --> 00:03:24,890 time was by their atomic mass. 69 00:03:24,890 --> 00:03:28,110 Atoms of different elements combine in simple whole-number 70 00:03:28,110 --> 00:03:30,600 ratios to form compounds. 71 00:03:30,600 --> 00:03:33,120 Well, that makes sense because they're the elements. 72 00:03:33,120 --> 00:03:34,750 They are the elemental building blocks. 73 00:03:34,750 --> 00:03:39,690 If I told you you could build a structure made of blocks and 74 00:03:39,690 --> 00:03:41,720 part-way through your construction I say, why don't 75 00:03:41,720 --> 00:03:44,210 you cut that block in half, you'd say, well, then the 76 00:03:44,210 --> 00:03:46,510 block isn't the building block. 77 00:03:46,510 --> 00:03:48,730 It's the half-block that's the building block. 78 00:03:48,730 --> 00:03:52,650 So axiomatically if these are the elements they must combine 79 00:03:52,650 --> 00:03:55,650 in simple whole-number ratios to form compounds. 80 00:03:55,650 --> 00:03:58,600 And lastly, atoms cannot be created or destroyed. 81 00:03:58,600 --> 00:04:01,180 Well, he wasn't foretelling E equals mc squared. 82 00:04:01,180 --> 00:04:03,700 What he was saying was that if you take elements and you 83 00:04:03,700 --> 00:04:06,620 combine them to form a compound, if you subsequently 84 00:04:06,620 --> 00:04:08,510 decompose the compound you get the elements 85 00:04:08,510 --> 00:04:10,690 back as they were. 86 00:04:10,690 --> 00:04:16,250 So those are the features of John Dalton's model. 87 00:04:16,250 --> 00:04:18,780 And we fast forward to 1869. 88 00:04:18,780 --> 00:04:22,520 And this is the knowledge that was available at the time in 89 00:04:22,520 --> 00:04:25,380 terms of the elements that had been isolated and 90 00:04:25,380 --> 00:04:26,500 characterized. 91 00:04:26,500 --> 00:04:28,220 And it was with this set of elements 92 00:04:28,220 --> 00:04:30,410 that Mendeleyev operated. 93 00:04:30,410 --> 00:04:34,250 On file cards, in his breast pocket, he carried with him 94 00:04:34,250 --> 00:04:35,150 everywhere. 95 00:04:35,150 --> 00:04:37,760 And he wrote down the names of the elements and their atomic 96 00:04:37,760 --> 00:04:42,620 masses and their properties and whatever else he could use 97 00:04:42,620 --> 00:04:44,510 the way of characterizing them. 98 00:04:44,510 --> 00:04:46,620 And during the course of writing a textbook-- 99 00:04:46,620 --> 00:04:50,250 he had just finished a chapter on the alkaline metals and he 100 00:04:50,250 --> 00:04:52,220 was sitting in the railway station playing 101 00:04:52,220 --> 00:04:53,780 solitaire, and boom! 102 00:04:53,780 --> 00:05:00,110 The flash came to him that you don't put arsenic underneath 103 00:05:00,110 --> 00:05:03,590 aluminum even though it's next in mass to zinc. You move it 104 00:05:03,590 --> 00:05:05,470 over and you don't even put it under silicon. 105 00:05:05,470 --> 00:05:06,840 You put it under phosphorus. 106 00:05:06,840 --> 00:05:09,680 And furthermore, what he said was there's going to be an 107 00:05:09,680 --> 00:05:13,780 element here discovered under silicon and it will have these 108 00:05:13,780 --> 00:05:14,410 properties. 109 00:05:14,410 --> 00:05:18,290 And let's look a little bit more deeply at the properties. 110 00:05:18,290 --> 00:05:23,870 But before doing so I want to say that by announcing this 111 00:05:23,870 --> 00:05:28,580 prediction of what the element should be that's missing is 112 00:05:28,580 --> 00:05:31,010 that we start to see the evolution of principles of 113 00:05:31,010 --> 00:05:31,930 modern chemistry. 114 00:05:31,930 --> 00:05:34,320 First of all, he recognized the pattern. 115 00:05:34,320 --> 00:05:36,060 So did Lothar Meyer in Tuebingen. 116 00:05:36,060 --> 00:05:39,090 So they both proposed a periodic table of the 117 00:05:39,090 --> 00:05:42,320 elements, but where Mendeleyev pulled away from the pack and 118 00:05:42,320 --> 00:05:44,250 distinguished himself was that he developed a 119 00:05:44,250 --> 00:05:45,880 quantitative model. 120 00:05:45,880 --> 00:05:48,000 And I haven't shown you the quantitative aspect yet. 121 00:05:48,000 --> 00:05:49,530 That's coming next. 122 00:05:49,530 --> 00:05:52,020 That explains the observations, and that's good. 123 00:05:52,020 --> 00:05:53,420 You might say, well, that's just curve 124 00:05:53,420 --> 00:05:54,880 fitting if you're a cynic. 125 00:05:54,880 --> 00:05:59,440 But it makes predictions that can be tested by experiment, 126 00:05:59,440 --> 00:06:01,360 tested by experiment. 127 00:06:01,360 --> 00:06:03,430 So let's take a look. 128 00:06:03,430 --> 00:06:06,950 He said that under silicon, but above tin, there would be 129 00:06:06,950 --> 00:06:07,420 an element. 130 00:06:07,420 --> 00:06:08,680 He called it eka-silicon. 131 00:06:08,680 --> 00:06:11,570 Eka is a Sanskrit word, which means one after. 132 00:06:11,570 --> 00:06:15,090 So this is the element one after silicon. 133 00:06:15,090 --> 00:06:19,610 It was eventually isolated and given the name germanium. 134 00:06:19,610 --> 00:06:21,770 Mendeleyev said it would have an atomic mass of 135 00:06:21,770 --> 00:06:23,200 72 grams per mole. 136 00:06:23,200 --> 00:06:25,640 In fact, it's 72.59. 137 00:06:25,640 --> 00:06:28,510 He said it would have a density of 5.5 grams per cubic 138 00:06:28,510 --> 00:06:29,060 centimeter. 139 00:06:29,060 --> 00:06:30,870 It's 5.36. 140 00:06:30,870 --> 00:06:33,462 This is 1869. 141 00:06:33,462 --> 00:06:35,940 He said that it would have a high melting point, whatever 142 00:06:35,940 --> 00:06:39,520 that means, and it melts at 958 Celsius. 143 00:06:39,520 --> 00:06:40,430 It's compounds. 144 00:06:40,430 --> 00:06:43,750 he said it would form a dioxide with a high melting 145 00:06:43,750 --> 00:06:45,660 point and a density of 4.7. 146 00:06:45,660 --> 00:06:49,590 It forms a dioxide and its density is 4.70. 147 00:06:49,590 --> 00:06:53,430 In fact, there's a story about a French mineralogist who came 148 00:06:53,430 --> 00:06:57,050 upon some of the stuff that ultimately became germanium 149 00:06:57,050 --> 00:07:01,200 dioxide, measured its density and reported it to Mendeleyev 150 00:07:01,200 --> 00:07:03,750 in a letter, saying, you know I measured the stuff and it's 151 00:07:03,750 --> 00:07:05,880 5.3 grams per cubic centimeter. 152 00:07:05,880 --> 00:07:07,960 Mendeleyev wrote him back and he said, make 153 00:07:07,960 --> 00:07:08,780 the measurement again. 154 00:07:08,780 --> 00:07:09,630 You're wrong. 155 00:07:09,630 --> 00:07:11,770 He wrote back three months later and said, 156 00:07:11,770 --> 00:07:12,870 I measured it again. 157 00:07:12,870 --> 00:07:14,620 It's 4.7. 158 00:07:14,620 --> 00:07:17,055 That was the genius of Mendeleyev. 159 00:07:17,055 --> 00:07:20,330 To go way out on a limb and make those predictions. 160 00:07:20,330 --> 00:07:23,960 And so I've made the case for the table of the elements. 161 00:07:23,960 --> 00:07:25,910 Why do we call it the Periodic Table? 162 00:07:25,910 --> 00:07:27,310 What's the periodic about? 163 00:07:27,310 --> 00:07:28,490 Well, the periodic-- 164 00:07:28,490 --> 00:07:31,430 take a look here, if you go to the website there's a tab 165 00:07:31,430 --> 00:07:35,040 called Courseware and there's a tab called Periodic Table. 166 00:07:35,040 --> 00:07:39,450 And you can go to the Periodic Table and ask the software to 167 00:07:39,450 --> 00:07:40,810 plot property. 168 00:07:40,810 --> 00:07:44,470 So for example this is boiling point versus proton number or 169 00:07:44,470 --> 00:07:45,690 atomic number. 170 00:07:45,690 --> 00:07:48,630 And so you see the boiling point varies as you move from 171 00:07:48,630 --> 00:07:50,630 low atomic number to high atomic number. 172 00:07:50,630 --> 00:07:52,110 But it's not totally random. 173 00:07:52,110 --> 00:07:54,290 It's not a Gaussian distribution. 174 00:07:54,290 --> 00:07:55,280 There are features. 175 00:07:55,280 --> 00:07:58,410 It goes up and down, up, down, up and down. 176 00:07:58,410 --> 00:08:01,180 If you train your eye a little bit you'll actually see some 177 00:08:01,180 --> 00:08:03,350 regularity, a pattern there. 178 00:08:03,350 --> 00:08:04,380 Maybe that's not so good. 179 00:08:04,380 --> 00:08:05,100 Let's look at this one. 180 00:08:05,100 --> 00:08:06,620 This is electrical conductivity. 181 00:08:06,620 --> 00:08:10,680 And again, up, down, up, down and look at those red lines. 182 00:08:10,680 --> 00:08:11,880 There, there, there, there. 183 00:08:11,880 --> 00:08:12,760 Don't you see something? 184 00:08:12,760 --> 00:08:14,020 That's a pattern. 185 00:08:14,020 --> 00:08:16,690 And they're almost equally spaced. 186 00:08:16,690 --> 00:08:20,720 So that was where Mendeleyev announced his Periodic Law, 187 00:08:20,720 --> 00:08:24,520 where he said the properties are related to the identity of 188 00:08:24,520 --> 00:08:29,930 the atoms. And furthermore, he announced, that the properties 189 00:08:29,930 --> 00:08:33,870 are a periodic variation in atomic mass. 190 00:08:33,870 --> 00:08:44,320 So let's get that now Mendeleyev's Periodic Law, and 191 00:08:44,320 --> 00:08:57,220 the properties of the elements vary 192 00:08:57,220 --> 00:09:04,960 periodically with atomic mass. 193 00:09:08,040 --> 00:09:09,290 That was Mendeleyev. 194 00:09:10,940 --> 00:09:17,010 So now that we know that we can go forward, and here's now 195 00:09:17,010 --> 00:09:21,010 the full-blown Periodic Table according to the framework 196 00:09:21,010 --> 00:09:22,250 that Mendeleyev established. 197 00:09:22,250 --> 00:09:24,520 Now if you look at this carefully, you'll see down 198 00:09:24,520 --> 00:09:27,600 here things get whited out and there's these strange 199 00:09:27,600 --> 00:09:30,000 notations, uu, m, and all that stuff. 200 00:09:30,000 --> 00:09:30,730 What's that all about? 201 00:09:30,730 --> 00:09:32,210 This is where the super heavies lie. 202 00:09:32,210 --> 00:09:34,190 These are all synthetic elements. 203 00:09:34,190 --> 00:09:39,820 Transuranic, they're made by high-energy reactions, 204 00:09:39,820 --> 00:09:44,250 so-called high-energy physics in what you might call 205 00:09:44,250 --> 00:09:48,020 accelerators, atom smashers, what have you. 206 00:09:48,020 --> 00:09:51,360 And there's only three places on the planet where you can 207 00:09:51,360 --> 00:09:54,340 conduct such reactions. 208 00:09:54,340 --> 00:09:59,510 One of them is in Darmstadt in Germany. 209 00:09:59,510 --> 00:10:02,860 One is in Dubna, just outside of Moscow. 210 00:10:02,860 --> 00:10:04,860 And if you want to stay home-- 211 00:10:04,860 --> 00:10:07,390 and eschew the frequent flyer miles-- you can go to 212 00:10:07,390 --> 00:10:08,550 Berkeley, California. 213 00:10:08,550 --> 00:10:11,690 These are the three places where we have the accelerators 214 00:10:11,690 --> 00:10:17,110 capable of making such compounds. 215 00:10:17,110 --> 00:10:22,210 And so, take a look carefully at what the nomenclature is. 216 00:10:22,210 --> 00:10:26,690 The way you name them is by using these Latin ordinals. 217 00:10:26,690 --> 00:10:29,420 So un, bi, tri, quad and so on. 218 00:10:29,420 --> 00:10:33,760 So if you wanted to name element 115, it's ununpentium. 219 00:10:33,760 --> 00:10:36,880 You want the ium ending. 220 00:10:36,880 --> 00:10:37,900 And you can make these up. 221 00:10:37,900 --> 00:10:40,730 You could make up element 205 if you want to or whatever. 222 00:10:40,730 --> 00:10:44,540 My favorite is 111 because that's unununium. 223 00:10:44,540 --> 00:10:49,760 But there they are, so you can have fun with those. 224 00:10:49,760 --> 00:10:55,870 But with time, the elements are being named and these have 225 00:10:55,870 --> 00:10:58,420 been synthesized since your version of 226 00:10:58,420 --> 00:11:00,080 the table was printed. 227 00:11:00,080 --> 00:11:05,080 And so number 110 is named Darmstadtium in honor of the 228 00:11:05,080 --> 00:11:07,820 team at Darmstadt that first isolated it. 229 00:11:07,820 --> 00:11:13,570 And number 111 was just named two years ago and the name is 230 00:11:13,570 --> 00:11:15,250 roentgenium after Wilhelm Roentgen, 231 00:11:15,250 --> 00:11:18,500 who discovered x-rays. 232 00:11:18,500 --> 00:11:19,940 Now what is it about discovery? 233 00:11:19,940 --> 00:11:26,060 Well, here's an example of one such reaction that would give 234 00:11:26,060 --> 00:11:27,650 you an element. 235 00:11:27,650 --> 00:11:31,550 So if we had access to one of these devices we could take, 236 00:11:31,550 --> 00:11:35,790 for example, lead and nickel and accelerate them to very, 237 00:11:35,790 --> 00:11:39,740 very high energies. 238 00:11:39,740 --> 00:11:42,790 And then we could make 110, ununilium. 239 00:11:42,790 --> 00:11:49,010 Or now we'll call it Darmstadtium plus neutron. 240 00:11:49,010 --> 00:11:54,170 And in doing so we've generated the new element. 241 00:11:54,170 --> 00:11:58,650 But we can't just say we've made the element and publish. 242 00:11:58,650 --> 00:12:01,470 We have to be able to characterize it. 243 00:12:01,470 --> 00:12:05,910 Remember the reason that we gave Cavendish the credit for 244 00:12:05,910 --> 00:12:08,590 discovering hydrogen wasn't that he's the first to know 245 00:12:08,590 --> 00:12:11,970 that hydrogen exists, but he isolated it and gave it value. 246 00:12:11,970 --> 00:12:14,120 So if you look at the rest of the periodic table, you get 247 00:12:14,120 --> 00:12:17,630 things like boiling point, melting point, density, 248 00:12:17,630 --> 00:12:20,070 electronegativity, first ionization energy. 249 00:12:20,070 --> 00:12:21,650 There's a lot of information there. 250 00:12:21,650 --> 00:12:23,000 If you go down here there's nothing. 251 00:12:23,000 --> 00:12:24,390 It's all blanks. 252 00:12:24,390 --> 00:12:27,810 These things have very, very short lifetimes. 253 00:12:27,810 --> 00:12:29,230 Fractions of a second. 254 00:12:29,230 --> 00:12:30,530 But you have to isolate them. 255 00:12:30,530 --> 00:12:32,930 There's certain criteria before you can publish. 256 00:12:32,930 --> 00:12:35,820 And all this is regulated by this governing body called the 257 00:12:35,820 --> 00:12:38,930 International Union of Pure and Applied Chemistry, So 258 00:12:38,930 --> 00:12:44,530 UPAC, the organization that finally rules on the 259 00:12:44,530 --> 00:12:46,240 legitimacy of any of these. 260 00:12:46,240 --> 00:12:48,450 And actually there have been some retractions in recent 261 00:12:48,450 --> 00:12:50,790 years, where people published claiming-- 262 00:12:50,790 --> 00:12:53,870 I think there was a report out of Berkeley claiming that 263 00:12:53,870 --> 00:12:57,170 they'd synthesized 115 and then subsequently that was 264 00:12:57,170 --> 00:13:01,060 retracted because they couldn't support the property 265 00:13:01,060 --> 00:13:02,870 measurements 266 00:13:02,870 --> 00:13:06,570 Last thing is, if you're interested, want to do some 267 00:13:06,570 --> 00:13:09,150 extra reading, there's a fantastic book about 268 00:13:09,150 --> 00:13:09,690 Mendeleyev. 269 00:13:09,690 --> 00:13:13,630 He was the youngest of 14 children, came out of a very 270 00:13:13,630 --> 00:13:18,380 poor family in Siberia and rose to be a giant of his day. 271 00:13:18,380 --> 00:13:20,490 He was a polymath. 272 00:13:20,490 --> 00:13:23,910 He, among some of the other things he did, he worked for 273 00:13:23,910 --> 00:13:28,485 the Ministry of Weights and Measures under the czar. 274 00:13:31,480 --> 00:13:35,270 The czar was interested in taxation of alcohol. 275 00:13:35,270 --> 00:13:41,150 And if you mix equal volumes of water and vodka you don't 276 00:13:41,150 --> 00:13:42,420 get additivity. 277 00:13:42,420 --> 00:13:46,460 So 100 mL of water plus 100 mL of vodka doesn't give 200 mL. 278 00:13:46,460 --> 00:13:47,680 It gives less. 279 00:13:47,680 --> 00:13:52,000 And so Mendeleyev did a study to determine what the optimum 280 00:13:52,000 --> 00:13:55,280 ratio is so that people couldn't misrepresent the 281 00:13:55,280 --> 00:13:58,340 amount of alcohol in the beverage. 282 00:13:58,340 --> 00:14:01,820 And set the standard at 40% alcohol by volume, which is 283 00:14:01,820 --> 00:14:03,700 used the world over to this day. 284 00:14:03,700 --> 00:14:08,170 He also came to the United States in 1876 to go to 285 00:14:08,170 --> 00:14:10,060 Titusville, Pennsylvania, where the first 286 00:14:10,060 --> 00:14:11,550 oil well was drilled. 287 00:14:11,550 --> 00:14:15,790 And did an exhaustive study of what was the American 288 00:14:15,790 --> 00:14:17,140 petroleum industry at the time. 289 00:14:17,140 --> 00:14:19,880 And then went back to Imperial Russia and did the same survey 290 00:14:19,880 --> 00:14:23,660 for the Czar in Imperial Russia, including a report 291 00:14:23,660 --> 00:14:26,370 that recommended how to develop the natural resources 292 00:14:26,370 --> 00:14:27,890 of the time. 293 00:14:27,890 --> 00:14:29,035 He was really an amazing man. 294 00:14:29,035 --> 00:14:31,100 He wrote text books and so on. 295 00:14:31,100 --> 00:14:34,730 And nobody in science-- 296 00:14:34,730 --> 00:14:36,890 I would venture to say-- has not heard of 297 00:14:36,890 --> 00:14:38,270 the periodic table. 298 00:14:38,270 --> 00:14:40,010 Mendeleyev died in 1906. 299 00:14:40,010 --> 00:14:42,760 The Nobel Prizes were first offered in 1901. 300 00:14:42,760 --> 00:14:48,560 So there were five years where he was close to the top for 301 00:14:48,560 --> 00:14:52,110 winning the Noble Prize but was eked out by somebody else. 302 00:14:52,110 --> 00:14:53,630 When you look back at those other Nobel 303 00:14:53,630 --> 00:14:55,450 Prizes, they were deserved. 304 00:14:55,450 --> 00:14:59,170 But none more so than that for Mendeleyev. 305 00:14:59,170 --> 00:15:04,420 So ironically the man who gave us seminal knowledge of all 306 00:15:04,420 --> 00:15:07,780 chemistry was never awarded the Nobel Prize. 307 00:15:07,780 --> 00:15:11,000 And there's probably a lot of politics in there. 308 00:15:11,000 --> 00:15:14,120 And as I said last day, here's the typical picture of him. 309 00:15:14,120 --> 00:15:16,280 In this he sort of looks like a street person, 310 00:15:16,280 --> 00:15:18,590 disheveled and so on. 311 00:15:18,590 --> 00:15:21,780 But this was the man that gave us the periodic table. 312 00:15:21,780 --> 00:15:26,580 That's him at age 35 when he annunciated the Periodic Law. 313 00:15:26,580 --> 00:15:28,680 So good for him. 314 00:15:28,680 --> 00:15:29,160 Alright. 315 00:15:29,160 --> 00:15:34,720 So now, let's take a look a little deeper about the 316 00:15:34,720 --> 00:15:36,070 properties of the elements. 317 00:15:36,070 --> 00:15:38,070 How do we understand the properties of the elements? 318 00:15:38,070 --> 00:15:39,820 For the properties elements we're going to have to look 319 00:15:39,820 --> 00:15:41,380 inside the atom. 320 00:15:41,380 --> 00:15:43,120 If you did your reading you undoubtedly 321 00:15:43,120 --> 00:15:44,790 came across this table. 322 00:15:44,790 --> 00:15:48,000 Which at first pass, deconstructs the atom into 323 00:15:48,000 --> 00:15:50,100 three simple particles: the electron, the 324 00:15:50,100 --> 00:15:51,690 proton and the neutron. 325 00:15:51,690 --> 00:15:54,220 Here are their symbols, e, p and n. 326 00:15:54,220 --> 00:15:58,080 And they're distinguished by charge and mass. 327 00:15:58,080 --> 00:16:02,030 So the electron has charge, minus 1.6 times 10 to the 328 00:16:02,030 --> 00:16:04,130 minus 19 Coulombs. 329 00:16:04,130 --> 00:16:07,940 And a very low mass: 9.11 times 10 to the minus 31 330 00:16:07,940 --> 00:16:11,360 kilograms. The electronic charge is balanced by the 331 00:16:11,360 --> 00:16:12,590 protonic charge. 332 00:16:12,590 --> 00:16:14,260 The atom is net neutral. 333 00:16:14,260 --> 00:16:18,060 So the proton has a charge of plus 1.6 times 10 to the minus 334 00:16:18,060 --> 00:16:19,540 19 Coulombs. 335 00:16:19,540 --> 00:16:22,920 The neutron, as the name implies, has 0 charge. 336 00:16:22,920 --> 00:16:25,350 The proton and the neutron have very nearly 337 00:16:25,350 --> 00:16:27,170 equal masses, however. 338 00:16:27,170 --> 00:16:27,530 Right. 339 00:16:27,530 --> 00:16:30,390 And just a word about the units. 340 00:16:30,390 --> 00:16:35,440 The units here are given in terms of the Systeme 341 00:16:35,440 --> 00:16:36,640 Internationale. 342 00:16:36,640 --> 00:16:40,140 So when we use the term, C, capital C is for the Coulomb. 343 00:16:43,230 --> 00:16:45,240 And that's the unit of charge. 344 00:16:45,240 --> 00:16:48,810 And it has an uppercase letter because it's named after a 345 00:16:48,810 --> 00:16:52,260 scientist. In this case, the French scientist, Coulomb, 346 00:16:52,260 --> 00:16:55,120 whereas the gram is not named after a 347 00:16:55,120 --> 00:16:57,790 scientist and so it's lowercase. 348 00:16:57,790 --> 00:17:00,210 And then we can amplify by powers of three. 349 00:17:00,210 --> 00:17:03,620 So if I want 1,000 of these, I put a lowercase k here. 350 00:17:03,620 --> 00:17:07,150 If I put an uppercase K, I end up with the unit Kelvin, which 351 00:17:07,150 --> 00:17:10,180 is the unit of temperature named after Lord Kelvin. 352 00:17:10,180 --> 00:17:14,880 And all of this is known as SI units, which is the 353 00:17:14,880 --> 00:17:16,100 International System. 354 00:17:16,100 --> 00:17:19,510 And it's not because the scientists don't know how to 355 00:17:19,510 --> 00:17:20,970 develop an abbreviation. 356 00:17:20,970 --> 00:17:23,720 This was originally developed when French was the 357 00:17:23,720 --> 00:17:26,180 international language of science. 358 00:17:26,180 --> 00:17:31,000 So this is known as the Systeme Internationale and all 359 00:17:31,000 --> 00:17:32,970 of these units were defined at that time. 360 00:17:32,970 --> 00:17:40,760 And the term SI sticks that's the legacy. 361 00:17:40,760 --> 00:17:43,810 All right, so now if we go to the Periodic Table. 362 00:17:43,810 --> 00:17:48,400 When we start looking at the elements, we can look at any 363 00:17:48,400 --> 00:17:51,340 entry on the Periodic Table, and we have the chemical 364 00:17:51,340 --> 00:18:00,260 symbol that I'm designating here as uppercase X, and this 365 00:18:00,260 --> 00:18:02,620 was originally John Dalton with the I and the 366 00:18:02,620 --> 00:18:03,890 circle around it. 367 00:18:03,890 --> 00:18:09,520 And about 30 years later the Swedish scientist Berzelius 368 00:18:09,520 --> 00:18:13,030 suggested that we use neutral units and so therefore we have 369 00:18:13,030 --> 00:18:16,920 the Latin coming in for many of the elements, such as iron, 370 00:18:16,920 --> 00:18:19,970 Fe, ferrum, and gold Au, aurum. 371 00:18:19,970 --> 00:18:23,430 In the upper-left corner, we have the quality I'm 372 00:18:23,430 --> 00:18:29,780 representing here, A And A is the mass number. 373 00:18:29,780 --> 00:18:31,960 Some people call it the atomic weight. 374 00:18:31,960 --> 00:18:34,470 And it is the sum of the masses of all the 375 00:18:34,470 --> 00:18:35,350 constituents. 376 00:18:35,350 --> 00:18:39,210 So it's the sum of the mass of the protons, so it's the 377 00:18:39,210 --> 00:18:43,360 proton number plus the neutron number plus 378 00:18:43,360 --> 00:18:44,390 the electron number. 379 00:18:44,390 --> 00:18:48,330 But since the electron weighs 1/1800 of what these others 380 00:18:48,330 --> 00:18:50,450 weigh, you normally don't consider this. 381 00:18:50,450 --> 00:18:51,240 It doesn't matter. 382 00:18:51,240 --> 00:18:55,870 So just adding protons plus neutrons gets you to what we 383 00:18:55,870 --> 00:18:57,290 call the atomic weight. 384 00:18:57,290 --> 00:19:02,420 And then down in the lower left corner we have Z and Z is 385 00:19:02,420 --> 00:19:03,850 the proton number. 386 00:19:09,070 --> 00:19:13,250 And as the name implies, it's equal to the number of protons 387 00:19:13,250 --> 00:19:20,200 in the nucleus, which then equals the number of electrons 388 00:19:20,200 --> 00:19:23,430 outside the nucleus in the neutral atom. 389 00:19:25,990 --> 00:19:30,360 Now I'm specifying neutral atom, because it's not 390 00:19:30,360 --> 00:19:32,820 necessary for atoms to be neutral and we'll take a look 391 00:19:32,820 --> 00:19:36,040 at those in a moment. 392 00:19:36,040 --> 00:19:37,690 A point about redundancy here. 393 00:19:37,690 --> 00:19:40,930 We don't really need the proton number and the chemical 394 00:19:40,930 --> 00:19:44,840 symbol because the proton number really defines. 395 00:19:44,840 --> 00:19:47,110 The proton number is like the Social Security number. 396 00:19:47,110 --> 00:19:53,820 This is the identity number of the atom. 397 00:19:53,820 --> 00:19:55,180 If we change the the proton number, 398 00:19:55,180 --> 00:19:58,200 we change its identity. 399 00:19:58,200 --> 00:20:01,360 So for example, I could write sodium. 400 00:20:01,360 --> 00:20:04,940 Sodium 23 and 11. 401 00:20:04,940 --> 00:20:06,220 I don't need the 11. 402 00:20:06,220 --> 00:20:09,410 11 means it's sodium or sodium means it's 11. 403 00:20:09,410 --> 00:20:13,080 So I could just write this as 23 sodium. 404 00:20:13,080 --> 00:20:15,860 So I know it's sodium, that means it's got 11 protons and 405 00:20:15,860 --> 00:20:18,220 23 minus 11 must be neutrons. 406 00:20:18,220 --> 00:20:20,050 Or if I wanted to be a smart aleck, I could 407 00:20:20,050 --> 00:20:22,030 write this : 23 11. 408 00:20:22,030 --> 00:20:22,880 That's sodium. 409 00:20:22,880 --> 00:20:25,640 I don't need to put anything here. 410 00:20:25,640 --> 00:20:29,850 But there's no smart alecks here, of course. 411 00:20:29,850 --> 00:20:34,980 So for example, we could then show this reaction as-- 412 00:20:34,980 --> 00:20:36,010 this is what? 413 00:20:36,010 --> 00:20:37,520 208. 414 00:20:37,520 --> 00:20:39,720 This is lead, 208. 415 00:20:39,720 --> 00:20:49,050 And nickel, 62 gives us Darmstadtium with a value of 416 00:20:49,050 --> 00:20:51,900 269 and the neutron is 1. 417 00:20:51,900 --> 00:20:56,450 You can see how these reactions can be made to go. 418 00:20:56,450 --> 00:21:01,130 Now atoms don't necessarily have to be net neutral. 419 00:21:01,130 --> 00:21:07,950 We can have something that is net non-zero charge. 420 00:21:07,950 --> 00:21:14,270 Net non-zero charge on the atom gives it the term, ion. 421 00:21:14,270 --> 00:21:17,740 Ion is an atom with net non-zero charge. 422 00:21:17,740 --> 00:21:22,810 And we have two cases where the atom is net positive. 423 00:21:22,810 --> 00:21:26,110 If the atom is net positive that's the result of electron 424 00:21:26,110 --> 00:21:27,780 deficiency. 425 00:21:27,780 --> 00:21:29,420 The atom is electron deficient. 426 00:21:32,020 --> 00:21:35,510 And we term such an atom the cation. 427 00:21:35,510 --> 00:21:36,750 There's two types of ions. 428 00:21:36,750 --> 00:21:38,100 The cation. 429 00:21:38,100 --> 00:21:41,740 And then we have something that is net negative. 430 00:21:41,740 --> 00:21:44,280 If it's net negative, it means it's electron-rich. 431 00:21:44,280 --> 00:21:48,660 That is to say, there are more electrons than protons and the 432 00:21:48,660 --> 00:21:52,370 net negative ion is called the anion. 433 00:21:52,370 --> 00:21:53,910 And you can try to figure out ways. 434 00:21:53,910 --> 00:21:57,120 I sometimes think that cation has a t, which looks a little 435 00:21:57,120 --> 00:21:59,420 bit like a plus sign. 436 00:21:59,420 --> 00:22:03,960 Anion has five letters, minus has five letters. 437 00:22:03,960 --> 00:22:06,980 And they both end in n, but this has an n, which is 438 00:22:06,980 --> 00:22:07,700 negative or something. 439 00:22:07,700 --> 00:22:08,950 You'll figure something out. 440 00:22:13,210 --> 00:22:16,420 Now we've talked about varying charge at 441 00:22:16,420 --> 00:22:19,300 constant proton number. 442 00:22:19,300 --> 00:22:21,750 But the other thing we can do is we can look at-- 443 00:22:21,750 --> 00:22:27,640 you can vary the neutron number. 444 00:22:27,640 --> 00:22:30,050 Since the neutron has no charge you can vary the 445 00:22:30,050 --> 00:22:32,350 neutron number and not harm the identity and still have a 446 00:22:32,350 --> 00:22:32,980 neutral atom. 447 00:22:32,980 --> 00:22:41,690 So vary neutron number at constant proton number. 448 00:22:41,690 --> 00:22:45,030 And let's see what that is. 449 00:22:45,030 --> 00:22:48,220 That gives you something that looks like this. 450 00:22:48,220 --> 00:22:52,480 So for example, if you if you look at carbon, the atomic 451 00:22:52,480 --> 00:22:56,100 mass that's shown here is 12.011. 452 00:22:56,100 --> 00:22:58,550 And you'd say, well, gee, if it's got 6 neutrons and 6 453 00:22:58,550 --> 00:23:01,130 protons, why isn't that 12 exactly? 454 00:23:01,130 --> 00:23:03,640 Well, this is the answer here. 455 00:23:03,640 --> 00:23:05,840 You can vary the neutron number at 456 00:23:05,840 --> 00:23:07,160 constant proton number. 457 00:23:07,160 --> 00:23:11,101 So let's take a look at how that plays out. 458 00:23:11,101 --> 00:23:14,660 The way that plays out is as following. 459 00:23:14,660 --> 00:23:16,930 Let's see I'm going to make a little table here. 460 00:23:24,580 --> 00:23:29,130 So we'll start with carbon 12. 461 00:23:29,130 --> 00:23:31,290 Carbon 12, so that means-- 462 00:23:31,290 --> 00:23:32,035 now I know what I'm going to do. 463 00:23:32,035 --> 00:23:37,820 I'm going to bring this down and make some headings for me. 464 00:23:37,820 --> 00:23:40,230 This will be my proton number and this will 465 00:23:40,230 --> 00:23:43,230 be my neutron number. 466 00:23:43,230 --> 00:23:45,180 And finally I'm going to talk about 467 00:23:45,180 --> 00:23:46,990 abundance, natural abundance. 468 00:23:49,560 --> 00:23:54,260 So carbon 12, since it's carbon, axiomatically it must 469 00:23:54,260 --> 00:23:55,850 have 6 protons. 470 00:23:55,850 --> 00:23:59,170 And 12 minus 6 is 6, so it's got 6 neutrons. 471 00:23:59,170 --> 00:24:02,260 And this is the dominant form of carbon. 472 00:24:02,260 --> 00:24:05,370 If you took a chemical analysis of the carbon you'd 473 00:24:05,370 --> 00:24:12,660 find that over 98%, 98.892% of the carbon atoms that you 474 00:24:12,660 --> 00:24:18,820 examined would be of this form, carbon 12. 475 00:24:18,820 --> 00:24:22,980 Now there's also carbon 13. 476 00:24:22,980 --> 00:24:25,660 Has to be 6, otherwise it's not carbon. 477 00:24:25,660 --> 00:24:27,690 That means it's got 7 neutrons. 478 00:24:27,690 --> 00:24:29,110 And it's a minority species. 479 00:24:29,110 --> 00:24:31,530 1.108%. 480 00:24:31,530 --> 00:24:34,490 And then there's a third form of carbon and 481 00:24:34,490 --> 00:24:36,310 that's carbon 14. 482 00:24:36,310 --> 00:24:40,870 Again, has to be 6 and it's got 8 neutrons. 483 00:24:40,870 --> 00:24:44,480 And it's found in vanishingly small quantities, one part in 484 00:24:44,480 --> 00:24:45,900 10 to the 12. 485 00:24:45,900 --> 00:24:50,710 Or we could call it ppt, parts per trillion. 486 00:24:50,710 --> 00:24:58,010 So this is same atomic number, same proton number, same Z but 487 00:24:58,010 --> 00:25:03,770 different mass numbers. 488 00:25:03,770 --> 00:25:04,960 Different A's. 489 00:25:04,960 --> 00:25:09,290 So all of these variants of carbon are found on the same 490 00:25:09,290 --> 00:25:12,120 place, the same spot on the Periodic Table. 491 00:25:12,120 --> 00:25:15,290 The Greek word for same is iso, and the word for place is 492 00:25:15,290 --> 00:25:18,370 topo, so these are called isotopes. 493 00:25:18,370 --> 00:25:22,970 The isotopes of carbon are species that have identical 494 00:25:22,970 --> 00:25:26,840 proton number but different neutron number. 495 00:25:26,840 --> 00:25:28,370 How about the units? 496 00:25:28,370 --> 00:25:29,650 What are the units here? 497 00:25:29,650 --> 00:25:32,620 Well, we have to give some kind of unit. 498 00:25:32,620 --> 00:25:36,790 I've been sort of freely going around and counting protons as 499 00:25:36,790 --> 00:25:37,740 one and so on. 500 00:25:37,740 --> 00:25:39,440 And here's the standard. 501 00:25:39,440 --> 00:25:48,330 The standard for mass is defined, and the definition 502 00:25:48,330 --> 00:25:49,720 goes like this. 503 00:25:49,720 --> 00:25:53,220 If you take carbon 12, which we just introduced to you, and 504 00:25:53,220 --> 00:25:58,580 we say that we're going to specify a mass of 12.000 grams 505 00:25:58,580 --> 00:26:05,400 exactly for a specified quantity, in other words, a 506 00:26:05,400 --> 00:26:08,850 specified number of these atoms. We have to say we'll 507 00:26:08,850 --> 00:26:13,550 take a certain number of these carbon atoms and specify the 508 00:26:13,550 --> 00:26:16,350 mass of that number is 12 exactly. 509 00:26:16,350 --> 00:26:23,680 And specified number of atoms being the mole. 510 00:26:23,680 --> 00:26:25,180 The mole. 511 00:26:25,180 --> 00:26:29,880 And it turns out that the mole has a value of 6.02 times 10 512 00:26:29,880 --> 00:26:30,900 to the 23rd. 513 00:26:30,900 --> 00:26:33,210 How do they get that number? 514 00:26:33,210 --> 00:26:37,300 A little bit more in the way of definitions. 515 00:26:37,300 --> 00:26:39,590 It was a concept put forth by a professor. 516 00:26:39,590 --> 00:26:41,660 So we're going to take some time on it because we respect 517 00:26:41,660 --> 00:26:45,870 professors, in this class at least. And so this was a 518 00:26:45,870 --> 00:26:51,400 concept put forth by Professor Amadeo Avogadro. 519 00:26:51,400 --> 00:26:55,580 Professor Avogadro, who was a professor of physics at the 520 00:26:55,580 --> 00:27:00,790 University of Turin, Torino. 521 00:27:00,790 --> 00:27:02,651 And he was a contemporary of John Dalton's and they were 522 00:27:02,651 --> 00:27:04,510 both studying gases. 523 00:27:04,510 --> 00:27:08,560 And it was Avogadro who taught us that, when you keep the 524 00:27:08,560 --> 00:27:11,860 pressure constant equal volumes of different gases 525 00:27:11,860 --> 00:27:14,250 contain equal numbers of molecules. 526 00:27:14,250 --> 00:27:17,980 It doesn't matter if you have argon, which is by itself 527 00:27:17,980 --> 00:27:21,180 atomic, or we have oxygen, which is diatomic, or you have 528 00:27:21,180 --> 00:27:25,360 methane, which is CH4, five atoms making a compound. 529 00:27:25,360 --> 00:27:27,740 Equal pressure, equal volume, equal 530 00:27:27,740 --> 00:27:29,270 numbers of those species. 531 00:27:29,270 --> 00:27:31,720 So that was Avogadro's Law. 532 00:27:31,720 --> 00:27:33,010 So let's put that down. 533 00:27:33,010 --> 00:27:46,160 At constant pressure equal volumes of different gases, 534 00:27:46,160 --> 00:27:51,340 contain identical numbers of atoms. Equal volumes of 535 00:27:51,340 --> 00:28:03,010 different gases contain equal numbers of molecules. 536 00:28:03,010 --> 00:28:06,280 And here I'm using the term molecule as a counting unit. 537 00:28:06,280 --> 00:28:08,690 So it could be, strictly speaking, an atom or it could 538 00:28:08,690 --> 00:28:10,800 be diatomic and so on. 539 00:28:10,800 --> 00:28:11,500 That's what it was. 540 00:28:11,500 --> 00:28:18,710 And out of honor for Avogadro, we name the number of atoms in 541 00:28:18,710 --> 00:28:20,950 the mole the Avogadro number. 542 00:28:20,950 --> 00:28:25,530 Which I've written 6.02 times 10 to the 23rd. 543 00:28:25,530 --> 00:28:28,220 Now how do we determine Avogadro's number? 544 00:28:28,220 --> 00:28:30,110 That's an interesting story. 545 00:28:30,110 --> 00:28:34,300 So first of all, we need two pieces of information. 546 00:28:34,300 --> 00:28:37,440 Because we're going to do this by the noblest form of 547 00:28:37,440 --> 00:28:39,480 chemistry, electrochemistry. 548 00:28:39,480 --> 00:28:42,210 So the first thing we're going to do is we're going to look 549 00:28:42,210 --> 00:28:49,090 at the work Michael Faraday in England. 550 00:28:49,090 --> 00:28:51,190 And what Michael Faraday did is he studied the 551 00:28:51,190 --> 00:28:53,200 electrodeposition of metal. 552 00:28:53,200 --> 00:28:57,470 And specifically he passed current through a cell and he 553 00:28:57,470 --> 00:28:59,850 electrodeposited silver. 554 00:28:59,850 --> 00:29:04,210 So he starts with silver plus, that's silver a cation, and by 555 00:29:04,210 --> 00:29:08,000 the action of electric current attaches an electron to silver 556 00:29:08,000 --> 00:29:09,790 and renders it neutral. 557 00:29:09,790 --> 00:29:14,820 Silver, which now plates out onto an electrode and they 558 00:29:14,820 --> 00:29:17,160 measured the mass. 559 00:29:17,160 --> 00:29:21,400 They measured the mass of silver-plated and they compare 560 00:29:21,400 --> 00:29:26,490 it to the amount of charge that was passed. 561 00:29:26,490 --> 00:29:27,740 They measured the charge. 562 00:29:30,430 --> 00:29:33,260 And you can get charge, because you know current. 563 00:29:33,260 --> 00:29:35,990 So charge is simply equal to the integral of the current 564 00:29:35,990 --> 00:29:36,830 times the time. 565 00:29:36,830 --> 00:29:38,560 You know the current, that's easy. 566 00:29:38,560 --> 00:29:47,030 And what Faraday found was that to make what we now know 567 00:29:47,030 --> 00:29:51,940 to be 108 grams of silver, 108 grams of silver, which we're 568 00:29:51,940 --> 00:29:55,010 going to subsequently recognize as the mole, which 569 00:29:55,010 --> 00:29:58,600 is identical to the amount, the number of particles in 108 570 00:29:58,600 --> 00:30:02,410 grams of silver, is equal to the number of particles in 12 571 00:30:02,410 --> 00:30:04,770 grams of carbon. 572 00:30:04,770 --> 00:30:08,690 Sort of an Avogadro-type harkening. 573 00:30:08,690 --> 00:30:10,330 He found that that is-- 574 00:30:10,330 --> 00:30:15,990 the equivalent requires 96,485 Coulombs. 575 00:30:15,990 --> 00:30:20,230 So you can say 1 mole of electrons gives me 1 mole of 576 00:30:20,230 --> 00:30:24,360 silver, so that's the charge on 1 mole of electrons, where 577 00:30:24,360 --> 00:30:28,210 Coulomb is the elementary charge, because we know 1 578 00:30:28,210 --> 00:30:35,390 electron per 1 silver atom deposited. 579 00:30:35,390 --> 00:30:38,620 So now if I know that's a mole of electrons, I need to find a 580 00:30:38,620 --> 00:30:41,270 charge on one electron, divide through and I get 581 00:30:41,270 --> 00:30:42,760 the Avogadro number. 582 00:30:42,760 --> 00:30:46,720 And to finish the story we have to wait about 50 years 583 00:30:46,720 --> 00:30:50,550 and come to the United States, where it's Robert Millikan, 584 00:30:50,550 --> 00:30:54,170 Robert Millikan at the University of Chicago doing 585 00:30:54,170 --> 00:30:58,130 the oil drop experiment through which we learn the 586 00:30:58,130 --> 00:30:59,540 elementary charge. 587 00:30:59,540 --> 00:31:02,550 And here's the cartoon of the oil drop experiment. 588 00:31:02,550 --> 00:31:04,085 I took this from a different text. 589 00:31:04,085 --> 00:31:05,940 It's not shown in your text. 590 00:31:05,940 --> 00:31:10,340 So I actually did this experiment as a sophomore at 591 00:31:10,340 --> 00:31:11,200 the University of Toronto. 592 00:31:11,200 --> 00:31:13,410 They had us repeat some of the great experiments of physics, 593 00:31:13,410 --> 00:31:14,700 the ones that were accessible, obviously. 594 00:31:14,700 --> 00:31:18,450 I couldn't do high-energy physics in an afternoon. 595 00:31:18,450 --> 00:31:20,350 That would have taken me a little bit longer. 596 00:31:20,350 --> 00:31:21,680 But we did this one. 597 00:31:21,680 --> 00:31:25,010 And so it consists of an atomizer, sort of a perfume 598 00:31:25,010 --> 00:31:28,360 atomizer, in which there's oil. 599 00:31:28,360 --> 00:31:33,000 And by the action of atomization we form a shower 600 00:31:33,000 --> 00:31:36,060 here, a very, very fine dispersion of 601 00:31:36,060 --> 00:31:37,680 tiny droplets of oil. 602 00:31:37,680 --> 00:31:41,200 And then-- this cartoon is hard to make sense of so I 603 00:31:41,200 --> 00:31:42,860 fixed this-- 604 00:31:42,860 --> 00:31:45,850 we shine high-energy radiation on this. 605 00:31:45,850 --> 00:31:48,440 And by the action of high energy radiation we take these 606 00:31:48,440 --> 00:31:51,730 neutral droplets and we turn them into ions. 607 00:31:51,730 --> 00:31:55,070 We eject electrons. 608 00:31:55,070 --> 00:31:57,340 And so now these are charged. 609 00:31:57,340 --> 00:32:00,730 And then we charge the plates. 610 00:32:00,730 --> 00:32:05,400 So if we have neutral species and they simply come out of 611 00:32:05,400 --> 00:32:08,020 the atomizer, they'll settle under gravity. 612 00:32:08,020 --> 00:32:12,090 But now if they're charged and I put a charge on the plates-- 613 00:32:12,090 --> 00:32:14,310 let's say as here the upper plate is positive-- 614 00:32:14,310 --> 00:32:17,385 if any of these particles is charged positive, the action 615 00:32:17,385 --> 00:32:21,140 of the electric field will accelerate the descent, 616 00:32:21,140 --> 00:32:23,420 because the bottom plate is negative attracting and a 617 00:32:23,420 --> 00:32:25,490 positive plate at the top is repelling. 618 00:32:25,490 --> 00:32:26,630 And vice versa. 619 00:32:26,630 --> 00:32:29,260 If I have a particle that's negative, the upper positive 620 00:32:29,260 --> 00:32:31,450 plate will actually cause it to slow down, and in the 621 00:32:31,450 --> 00:32:33,850 extreme, it may actually start to rise. 622 00:32:33,850 --> 00:32:37,490 And so what Millikan did is a set of experiments in which he 623 00:32:37,490 --> 00:32:39,880 studied all the different particle sizes. 624 00:32:39,880 --> 00:32:41,110 See this telescope? 625 00:32:41,110 --> 00:32:43,170 Right over here is Millikan. 626 00:32:43,170 --> 00:32:44,790 And Millikan's sitting there and he's 627 00:32:44,790 --> 00:32:46,240 squirting and he's watching. 628 00:32:46,240 --> 00:32:48,610 He's measuring the settling velocity. 629 00:32:48,610 --> 00:32:51,370 And he changes the magnitude of the electric field. 630 00:32:51,370 --> 00:32:53,590 He changes the intensity of radiation. 631 00:32:53,590 --> 00:32:55,255 He changes the nozzle. 632 00:32:55,255 --> 00:32:56,960 He changes everything he can. 633 00:32:56,960 --> 00:32:58,090 And what does he find? 634 00:32:58,090 --> 00:33:01,460 He finds that the distribution of velocities is not 635 00:33:01,460 --> 00:33:03,200 continuous. 636 00:33:03,200 --> 00:33:04,750 It's not continuous. 637 00:33:04,750 --> 00:33:07,580 You think, well, gee if you just keep dialing you should 638 00:33:07,580 --> 00:33:10,020 get every variation of velocity. 639 00:33:10,020 --> 00:33:11,060 Well, he doesn't. 640 00:33:11,060 --> 00:33:17,690 He finds that he gets variation down to a single 641 00:33:17,690 --> 00:33:20,700 value, below which he can't go. 642 00:33:20,700 --> 00:33:32,440 He determines that electric charge is quantized. 643 00:33:32,440 --> 00:33:35,080 That is to say there's a base unit. 644 00:33:35,080 --> 00:33:36,310 It's an element. 645 00:33:36,310 --> 00:33:39,910 I just talked to you about the elemental building block. 646 00:33:39,910 --> 00:33:42,470 That's an element in mass space. 647 00:33:42,470 --> 00:33:43,170 Now I'm going to go 648 00:33:43,170 --> 00:33:45,790 conceptually into charge space. 649 00:33:45,790 --> 00:33:49,655 There is an elemental building block of electric charge. 650 00:33:52,280 --> 00:33:53,840 Electric charge is quantized. 651 00:33:57,950 --> 00:34:06,450 And he found that the elementary charge, which we 652 00:34:06,450 --> 00:34:08,270 gave the symbol, e. 653 00:34:08,270 --> 00:34:10,430 e is not the symbol for electron. 654 00:34:10,430 --> 00:34:12,580 e is the symbol for elementary charge. 655 00:34:12,580 --> 00:34:18,030 It has a value, if you convert it to modern SI units, of 1.6 656 00:34:18,030 --> 00:34:24,385 times 10 to the minus 19 Coulombs. 657 00:34:24,385 --> 00:34:28,960 So now I can take these two pieces of information, Faraday 658 00:34:28,960 --> 00:34:31,210 which is up here. 659 00:34:31,210 --> 00:34:34,190 This is known as the Faraday Constant. 660 00:34:34,190 --> 00:34:38,810 Script f, Faraday constant. 661 00:34:38,810 --> 00:34:41,440 So if I divide the Faraday constant, which is the charge 662 00:34:41,440 --> 00:34:44,470 on a mole of electrons, by the elementary charge, which is 663 00:34:44,470 --> 00:34:48,010 the charge on one electron, presumably I should end up 664 00:34:48,010 --> 00:34:49,350 with the Avogadro number. 665 00:34:49,350 --> 00:34:52,890 It should be the ratio of the Faraday to 666 00:34:52,890 --> 00:34:54,110 the elementary charge. 667 00:34:54,110 --> 00:34:55,570 And it gives us-- 668 00:34:55,570 --> 00:34:56,890 for the third time this morning-- 669 00:34:56,890 --> 00:35:00,190 6.02 times 10 to the 23rd. 670 00:35:00,190 --> 00:35:06,590 If you like per mole, yes or no, doesn't matter. 671 00:35:06,590 --> 00:35:09,050 So now, what's the atomic mass unit? 672 00:35:09,050 --> 00:35:13,650 Now we can say the atomic mass unit is, 1 atomic mass unit 673 00:35:13,650 --> 00:35:15,370 then must equal what? 674 00:35:15,370 --> 00:35:22,590 It's going to equal 1/12 of the mass of carbon 12. 675 00:35:22,590 --> 00:35:27,420 1/12 of the mass of carbon 12 divided by the Avogadro 676 00:35:27,420 --> 00:35:34,900 number, which gives us 1.661 times 10 to the minus 27 677 00:35:34,900 --> 00:35:36,320 kilograms. 678 00:35:36,320 --> 00:35:39,500 Now be careful because the system is just 679 00:35:39,500 --> 00:35:40,450 a little bit rickety. 680 00:35:40,450 --> 00:35:44,590 You know we went SI, but look, this is still defined as 12 681 00:35:44,590 --> 00:35:49,900 grams. And so sometimes if you look depending on where this 682 00:35:49,900 --> 00:35:54,510 is, 10 to minus 27 kilograms or 10 to the minus 24 grams. 683 00:35:54,510 --> 00:35:55,760 Just be careful. 684 00:35:58,260 --> 00:36:05,040 If you ignore this you'll be off only by factor of 1,000. 685 00:36:05,040 --> 00:36:05,730 That's a joke. 686 00:36:05,730 --> 00:36:08,250 But it's lost here. 687 00:36:08,250 --> 00:36:09,410 People are too serious. 688 00:36:09,410 --> 00:36:10,660 We'll lighten you up. 689 00:36:10,660 --> 00:36:13,420 All right, so enough of the history. 690 00:36:13,420 --> 00:36:15,100 Let's now do something dynamic. 691 00:36:15,100 --> 00:36:16,930 So far we've been studying static elements. 692 00:36:16,930 --> 00:36:21,010 But chemistry is really the action of elements in motion. 693 00:36:21,010 --> 00:36:24,060 So how do we describe a chemical reaction? 694 00:36:24,060 --> 00:36:25,080 Let's look at that. 695 00:36:25,080 --> 00:36:29,090 What are the rules to describe a chemical reaction? 696 00:36:29,090 --> 00:36:31,190 Write an equation. 697 00:36:31,190 --> 00:36:36,179 Write the equation of the chemical reaction subject to 698 00:36:36,179 --> 00:36:38,167 these rules. 699 00:36:38,167 --> 00:36:40,652 There are two simple rules. 700 00:36:40,652 --> 00:36:45,544 One is conservation of mass. 701 00:36:45,544 --> 00:36:45,712 We've been told the repeatedly since Democritus, 702 00:36:45,712 --> 00:36:47,740 conservation of mass. 703 00:36:47,740 --> 00:36:51,440 And the second thing, we use Dalton's Law of Molar 704 00:36:51,440 --> 00:36:52,690 Proportions. 705 00:36:58,120 --> 00:37:02,750 That is to say, the building blocks in integer ratios. 706 00:37:06,380 --> 00:37:08,950 And so I thought I'd do this in context. 707 00:37:08,950 --> 00:37:11,710 So I've got a specific example here. 708 00:37:11,710 --> 00:37:13,940 So this is something that I'm interested in. 709 00:37:13,940 --> 00:37:17,810 Some of my research is in metallurgical extraction by 710 00:37:17,810 --> 00:37:18,910 benign processes. 711 00:37:18,910 --> 00:37:21,400 What you're looking at is a billet of titanium. 712 00:37:21,400 --> 00:37:23,470 To give you a sense, you can see the stairwell back here. 713 00:37:23,470 --> 00:37:26,770 So this is about 4 feet, a little over a meter here. 714 00:37:26,770 --> 00:37:29,720 So you can see this is one honking big piece of titanium. 715 00:37:29,720 --> 00:37:32,890 This came out of the primary reactor, the Kroll reactor and 716 00:37:32,890 --> 00:37:36,910 this is subsequently swaged and hot worked and so on to 717 00:37:36,910 --> 00:37:37,760 form these billets. 718 00:37:37,760 --> 00:37:41,920 So this is the first step of turning dirt into metal. 719 00:37:41,920 --> 00:37:43,285 That's called titanium sponge. 720 00:37:43,285 --> 00:37:48,550 And titanium sponge occurs inside a Kroll reactor. 721 00:37:48,550 --> 00:37:51,780 It occurs inside a Kroll reactor, which was invented by 722 00:37:51,780 --> 00:37:56,440 a man of the surname Kroll in Luxembourg in the 1930s. 723 00:37:56,440 --> 00:37:59,870 And then with the advent of World War II, he decided to be 724 00:37:59,870 --> 00:38:01,120 smart, to get out. 725 00:38:01,120 --> 00:38:04,190 And he ended up in Oregon where he became a professor. 726 00:38:04,190 --> 00:38:06,580 So he's known as Professor Kroll, although the truth be 727 00:38:06,580 --> 00:38:08,560 told he really made his discovery 728 00:38:08,560 --> 00:38:09,820 before he became a professor. 729 00:38:09,820 --> 00:38:12,380 But he's still a professor and so we'll honor him. 730 00:38:12,380 --> 00:38:19,970 And so the Kroll process for making titanium centers around 731 00:38:19,970 --> 00:38:21,200 this reaction. 732 00:38:21,200 --> 00:38:27,280 Here's the reaction written according to the rules above. 733 00:38:27,280 --> 00:38:30,460 We take titanium dioxide, which is found in the Earth 734 00:38:30,460 --> 00:38:33,910 and by some prior chemistry convert it to titanium 735 00:38:33,910 --> 00:38:37,200 tetrachloride, and in a reactor that I'm going to show 736 00:38:37,200 --> 00:38:39,190 you in a moment, we react titanium 737 00:38:39,190 --> 00:38:41,150 tetrachloride with magnesium. 738 00:38:41,150 --> 00:38:44,040 And magnesium has a higher affinity for chlorine than 739 00:38:44,040 --> 00:38:48,660 does titanium and steals the chlorine from titanium to form 740 00:38:48,660 --> 00:38:53,130 magnesium chloride, leaving behind titanium metal. 741 00:38:53,130 --> 00:38:55,760 Now we have to have conservation of mass. 742 00:38:55,760 --> 00:38:58,860 So you can see, I've got 4 chlorines on the left but only 743 00:38:58,860 --> 00:39:00,130 2 chlorines on the right. 744 00:39:00,130 --> 00:39:02,930 So I'm going to put a 2 here and double 745 00:39:02,930 --> 00:39:04,140 the magnesium chloride. 746 00:39:04,140 --> 00:39:06,070 But now I've got 2 magnesiums on the right and 747 00:39:06,070 --> 00:39:07,330 only 1 on the left. 748 00:39:07,330 --> 00:39:09,920 So I'll put a 2 in front of the magnesium and now we have 749 00:39:09,920 --> 00:39:11,170 a balanced equation. 750 00:39:14,100 --> 00:39:17,580 And here's what the reactor looks like. 751 00:39:17,580 --> 00:39:21,370 You can imagine a giant vessel with a pressure seal on the 752 00:39:21,370 --> 00:39:24,660 top and a couple of valves, big enough to make this. 753 00:39:24,660 --> 00:39:27,900 So this is about 15 feet by 30 feet. 754 00:39:27,900 --> 00:39:32,210 And so we introduce titanium tetrachloride, which is a gas, 755 00:39:32,210 --> 00:39:36,760 and magnesium as a solid and heat to 900 degrees C. 756 00:39:36,760 --> 00:39:39,310 And at 900 degrees C, if you look on your Periodic Table 757 00:39:39,310 --> 00:39:42,450 you'll know that magnesium melts at 650 degrees C. 758 00:39:42,450 --> 00:39:45,250 So we have a liquid sitting here, titanium tetrachloride 759 00:39:45,250 --> 00:39:47,830 here, and this thing is sealed. 760 00:39:47,830 --> 00:39:49,550 It's called a bomb reactor. 761 00:39:49,550 --> 00:39:51,190 Nothing can get in, nothing can get out. 762 00:39:51,190 --> 00:39:52,630 The pressure builds up here. 763 00:39:52,630 --> 00:39:55,100 And right at this interface the titanium tetrachloride 764 00:39:55,100 --> 00:39:57,840 reacts with the magnesium according to this reaction. 765 00:39:57,840 --> 00:39:59,280 Now this is very interesting. 766 00:39:59,280 --> 00:40:01,530 It's beautiful reaction because the titanium 767 00:40:01,530 --> 00:40:04,880 tetrachloride is a gas; magnesium is a liquid. 768 00:40:04,880 --> 00:40:07,740 Magnesium chloride is a liquid, but it is of different 769 00:40:07,740 --> 00:40:11,300 density, and it is insoluble in magnesium, and titanium 770 00:40:11,300 --> 00:40:13,620 melts at 1670 and it's a solid. 771 00:40:13,620 --> 00:40:16,260 So what happens over time is this. 772 00:40:16,260 --> 00:40:19,920 The magnesium chloride that forms pools underneath the 773 00:40:19,920 --> 00:40:22,790 magnesium liquid, gets out of the way so that we can 774 00:40:22,790 --> 00:40:25,750 continue to keep this interface clean and have the 775 00:40:25,750 --> 00:40:26,970 reaction proceed. 776 00:40:26,970 --> 00:40:31,630 You don't want to reaction where reactant A reacts with 777 00:40:31,630 --> 00:40:34,710 reactant B, makes a product that covers the interface and 778 00:40:34,710 --> 00:40:38,000 now the product is in the way of future reaction. 779 00:40:38,000 --> 00:40:40,760 So this is very elegant because I don't need any fans, 780 00:40:40,760 --> 00:40:43,420 I don't need any nose propellers, nothing. 781 00:40:43,420 --> 00:40:46,110 By density the magnesium chloride settles and the 782 00:40:46,110 --> 00:40:47,370 titanium settles. 783 00:40:47,370 --> 00:40:48,740 And it's sitting here at the bottom. 784 00:40:48,740 --> 00:40:51,010 And you can imagine if we do this long enough, this 785 00:40:51,010 --> 00:40:54,120 titanium at the bottom will continue to build until it 786 00:40:54,120 --> 00:40:56,190 looks like this. 787 00:40:56,190 --> 00:40:59,342 As long as you keep feeding TiCl and Mg. 788 00:40:59,342 --> 00:41:01,160 See I'm talking metallurgy now. 789 00:41:01,160 --> 00:41:04,980 TiCl and Mg, that's what you make. 790 00:41:04,980 --> 00:41:08,350 So that's how we make titanium, first step. 791 00:41:08,350 --> 00:41:12,120 And so suppose you get hired and it's your first day on the 792 00:41:12,120 --> 00:41:19,500 job and you're working at Cambridge Titanium and the 793 00:41:19,500 --> 00:41:29,160 boss says let's put in 200 kilograms of TiCl and we'll 794 00:41:29,160 --> 00:41:34,060 put in 25 kilograms of Mg. 795 00:41:34,060 --> 00:41:38,590 And the question is, what is the yield? 796 00:41:38,590 --> 00:41:39,670 What is the yield? 797 00:41:39,670 --> 00:41:42,590 How much titanium are we going to make? 798 00:41:42,590 --> 00:41:44,240 Well, you say, just multiply it out. 799 00:41:44,240 --> 00:41:47,940 But first you have to see if things are in balance. 800 00:41:47,940 --> 00:41:52,410 We have to study the stoichiometry of the reaction. 801 00:41:52,410 --> 00:41:54,260 Stoichiometry, what does this mean? 802 00:41:54,260 --> 00:41:56,590 It's from the Greek, stoicheia, which has to do 803 00:41:56,590 --> 00:41:59,300 with measurement proportions. 804 00:41:59,300 --> 00:42:04,740 So if these are not put in to the reactor in proportion to 805 00:42:04,740 --> 00:42:07,360 what they are in the equation we're not going to get the 806 00:42:07,360 --> 00:42:08,870 yield here. 807 00:42:08,870 --> 00:42:12,250 So first thing I gotta do, this is in moles, this is in 808 00:42:12,250 --> 00:42:15,700 kilograms. So I have to convert the kilograms to moles 809 00:42:15,700 --> 00:42:17,660 and then maybe I can make some sense of this. 810 00:42:17,660 --> 00:42:21,255 So if I divide by the atomic mass of titanium, four times 811 00:42:21,255 --> 00:42:24,910 the atomic mass of chlorine and convert; I will discover 812 00:42:24,910 --> 00:42:30,770 that I have 1,054 moles of TiCl. 813 00:42:30,770 --> 00:42:36,770 And I've got about 1,029 moles of magnesium. 814 00:42:36,770 --> 00:42:43,170 Well, this equation says I need 2 times the amount of 815 00:42:43,170 --> 00:42:44,160 titanium tetrachloride. 816 00:42:44,160 --> 00:42:47,180 Well, it's obvious to the naked eye, 1,029 isn't two 817 00:42:47,180 --> 00:42:49,150 times 1,054. 818 00:42:49,150 --> 00:42:50,690 So I've got a problem here. 819 00:42:50,690 --> 00:42:54,290 I'm not going to get as much titanium as I put in. 820 00:42:54,290 --> 00:42:55,540 Titanium chloride. 821 00:42:55,540 --> 00:42:57,930 This yield is going to be restricted. 822 00:42:57,930 --> 00:43:00,510 It's going to be restricted by-- this is sort of a chain 823 00:43:00,510 --> 00:43:02,420 is as strong as its weakest link-- 824 00:43:02,420 --> 00:43:06,910 the yield is restricted by the amount of limiting reagent. 825 00:43:06,910 --> 00:43:11,820 And in this case, magnesium is-- this is less than 2 times 826 00:43:11,820 --> 00:43:15,630 the mole number of titanium chloride. 827 00:43:15,630 --> 00:43:17,950 So this means this is the limiting reagent. 828 00:43:22,510 --> 00:43:26,470 Alright so now if we use that principle then I'm only going 829 00:43:26,470 --> 00:43:28,910 to get as much titanium as I had magnesium and you can see 830 00:43:28,910 --> 00:43:32,140 from the stoichiometry here, if I've got 1,029 moles of 831 00:43:32,140 --> 00:43:33,800 magnesium I'm going to have half of 832 00:43:33,800 --> 00:43:35,510 that number of titanium. 833 00:43:35,510 --> 00:43:42,430 So therefore the amount of titanium is equal to 515 moles 834 00:43:42,430 --> 00:43:43,410 of titanium. 835 00:43:43,410 --> 00:43:46,730 And you notice I'm not obsessed about a significant 836 00:43:46,730 --> 00:43:47,600 figures and so on. 837 00:43:47,600 --> 00:43:49,980 It's a metallurgical plant. 838 00:43:49,980 --> 00:43:51,990 Half of 1,029 is 515. 839 00:43:51,990 --> 00:43:53,900 Is it 514.5? 840 00:43:53,900 --> 00:43:54,590 If you wish. 841 00:43:54,590 --> 00:43:55,060 I don't care. 842 00:43:55,060 --> 00:43:59,330 So 515 moles and then I convert that, which gives me 843 00:43:59,330 --> 00:44:05,430 24.7 kilograms of titanium when I use 844 00:44:05,430 --> 00:44:07,240 that amount of magnesium. 845 00:44:07,240 --> 00:44:11,720 And if you go to the text, Section 2.7, you'll see the 846 00:44:11,720 --> 00:44:14,580 nuts and bolts of how to run these reactions. 847 00:44:14,580 --> 00:44:16,355 For those of you who had a lot of chemistry in high school, I 848 00:44:16,355 --> 00:44:18,900 know this is review, but I want to bring everybody up to 849 00:44:18,900 --> 00:44:20,600 the same page. 850 00:44:20,600 --> 00:44:23,530 So we're starting with this. 851 00:44:23,530 --> 00:44:24,070 All right. 852 00:44:24,070 --> 00:44:26,940 I think that's a pretty good place to 853 00:44:26,940 --> 00:44:28,930 stop with the delivery. 854 00:44:28,930 --> 00:44:31,130 But I don't want you moving. 855 00:44:31,130 --> 00:44:31,690 You don't move yet. 856 00:44:31,690 --> 00:44:33,080 Because the last 5 minutes I'm going to 857 00:44:33,080 --> 00:44:34,150 still continue to talk. 858 00:44:34,150 --> 00:44:36,040 But on a slightly different topic. 859 00:44:36,040 --> 00:44:38,320 And so I don't want to hear the binders 860 00:44:38,320 --> 00:44:41,020 snapping and so on. 861 00:44:41,020 --> 00:44:42,590 We're here; you paid your money. 862 00:44:42,590 --> 00:44:44,150 Five more minutes. 863 00:44:44,150 --> 00:44:46,090 Five more minutes and then you're out there. 864 00:44:46,090 --> 00:44:48,200 Out there, then begins le weekend. 865 00:44:48,200 --> 00:44:49,820 But not until then. 866 00:44:49,820 --> 00:44:51,260 So a couple of things. 867 00:44:51,260 --> 00:44:52,960 First is, the music today. 868 00:44:52,960 --> 00:44:54,760 I try to link the music thematically. 869 00:44:54,760 --> 00:45:01,260 So the music playing today was Polovstian Dance number 17 870 00:45:01,260 --> 00:45:05,510 from Prince Igor, by Borodin, Aleksandr Borodin. 871 00:45:05,510 --> 00:45:07,210 Why were we listening to this music? 872 00:45:07,210 --> 00:45:09,870 Well, because I insisted that we listen to it. 873 00:45:09,870 --> 00:45:11,060 Well, what about Borodin? 874 00:45:11,060 --> 00:45:13,270 Borodin lived in Saint Petersburg. 875 00:45:13,270 --> 00:45:14,860 He was a friend of Mendeleyev. 876 00:45:14,860 --> 00:45:19,100 OK, that's cute but more importantly Borodin wrote his 877 00:45:19,100 --> 00:45:20,930 music in his leisure time. 878 00:45:20,930 --> 00:45:22,050 He had a day job. 879 00:45:22,050 --> 00:45:25,690 His day job was professor of chemistry. 880 00:45:25,690 --> 00:45:28,570 And he worked at the Medical Surgical Academy in Saint 881 00:45:28,570 --> 00:45:29,630 Petersburg. 882 00:45:29,630 --> 00:45:31,920 He was an exceptional human being. 883 00:45:31,920 --> 00:45:34,980 In those days, women were forbidden to attend 884 00:45:34,980 --> 00:45:36,830 institutions of higher education. 885 00:45:36,830 --> 00:45:42,190 He set up an entire curriculum for women in a night school at 886 00:45:42,190 --> 00:45:44,710 the Medical Surgical Academy. 887 00:45:44,710 --> 00:45:47,560 He cavorted with artists and therefore obviously his 888 00:45:47,560 --> 00:45:48,810 politics were radical. 889 00:45:48,810 --> 00:45:51,890 And they were trying to reform the political scene in Czarist 890 00:45:51,890 --> 00:45:53,440 Russia at the time. 891 00:45:53,440 --> 00:45:56,700 And he was also quite a bon vivant. 892 00:45:56,700 --> 00:46:03,080 And he died on his feet dancing at a ball. 893 00:46:03,080 --> 00:46:04,570 So that's the way to go. 894 00:46:04,570 --> 00:46:06,200 Having a great time. 895 00:46:06,200 --> 00:46:07,450 That was Borodin. 896 00:46:09,590 --> 00:46:11,160 One other thing before you go. 897 00:46:11,160 --> 00:46:14,680 You were very very dour, so I thought I'd try to put you in 898 00:46:14,680 --> 00:46:17,800 a good mood to the extent this is possible with this group. 899 00:46:17,800 --> 00:46:22,050 And I wanted to share with you some news. 900 00:46:22,050 --> 00:46:23,780 There's been a new element discovered. 901 00:46:23,780 --> 00:46:26,640 You know these atoms smashers, they're always working. 902 00:46:26,640 --> 00:46:29,340 And so the discovery of the heaviest element known to 903 00:46:29,340 --> 00:46:31,170 science has been reported. 904 00:46:31,170 --> 00:46:33,750 The element, tentatively named administratium. 905 00:46:36,900 --> 00:46:39,530 I don't know if UPEC is going to go for this, but you can 906 00:46:39,530 --> 00:46:41,910 suggest names. 907 00:46:41,910 --> 00:46:44,430 So they're going to name is administratium, the 908 00:46:44,430 --> 00:46:47,240 discoverers. 909 00:46:47,240 --> 00:46:50,830 It has no protons or electrons. 910 00:46:50,830 --> 00:46:55,500 So that means its atomic number is 0. 911 00:46:55,500 --> 00:47:00,850 It does have one neutron, 125 assistants to the neutron. 912 00:47:00,850 --> 00:47:04,820 75 vice-neutrons and a 111 assistants to the 913 00:47:04,820 --> 00:47:06,360 vice-neutrons. 914 00:47:06,360 --> 00:47:11,580 This gives it a mass number of 312. 915 00:47:11,580 --> 00:47:14,660 The 312 particles are held together in the nucleus by a 916 00:47:14,660 --> 00:47:17,210 force that involves the continuous exchange of 917 00:47:17,210 --> 00:47:21,430 meson-like particles called memo-ons. 918 00:47:21,430 --> 00:47:24,470 There's no electronic mail, because there's no electrons. 919 00:47:24,470 --> 00:47:27,220 There may be neutronic mail but we don't know yet. 920 00:47:27,220 --> 00:47:29,110 Now you've already learned something today. 921 00:47:29,110 --> 00:47:30,220 You know something. 922 00:47:30,220 --> 00:47:32,640 Since it has no electrons, what do we know about its 923 00:47:32,640 --> 00:47:34,820 chemical reactivity? 924 00:47:34,820 --> 00:47:35,805 It's inert. 925 00:47:35,805 --> 00:47:37,080 It has no electrons. 926 00:47:37,080 --> 00:47:38,230 It can't exchange. 927 00:47:38,230 --> 00:47:39,450 So this is chemically inert. 928 00:47:39,450 --> 00:47:42,920 So you say, how did they detect it? 929 00:47:42,920 --> 00:47:44,940 Because it seems to impede every reaction in 930 00:47:44,940 --> 00:47:46,190 which it is a present. 931 00:47:49,290 --> 00:47:53,010 According to the discoverers a few nanograms rendered a 932 00:47:53,010 --> 00:47:58,420 reaction that normally takes a fraction of a second, it took 933 00:47:58,420 --> 00:48:01,635 now four business days to conduct that same. 934 00:48:04,450 --> 00:48:07,370 There are a few other properties. 935 00:48:07,370 --> 00:48:10,030 We know so far that it's radioactive. 936 00:48:10,030 --> 00:48:11,990 And we're going to study radioactivity later, so 937 00:48:11,990 --> 00:48:13,830 there's a little bit of foreshadowing. 938 00:48:13,830 --> 00:48:16,850 It has a half-life of about three years, at which time it 939 00:48:16,850 --> 00:48:22,240 stops decaying and instead it undergoes a reorganization, in 940 00:48:22,240 --> 00:48:24,780 which the vice-neutrons, assistants to the neutrons and 941 00:48:24,780 --> 00:48:25,310 assistants to the 942 00:48:25,310 --> 00:48:27,810 vice-neutrons, exchange places. 943 00:48:27,810 --> 00:48:32,040 Some studies indicate that the mass actually increases after 944 00:48:32,040 --> 00:48:33,760 each reorganization. 945 00:48:33,760 --> 00:48:36,970 So you can imagine now we'll have something like this. 946 00:48:40,590 --> 00:48:43,270 See how this increased? 947 00:48:43,270 --> 00:48:47,370 So if they occupy the same place, they have the same 948 00:48:47,370 --> 00:48:51,110 proton number, but a different neutron number, in the case of 949 00:48:51,110 --> 00:48:55,080 administratium, they're called isodopes. 950 00:48:55,080 --> 00:48:57,820 So with that I will say, have a good weekend.