WEBVTT 00:00:00.030 --> 00:00:02.400 The following content is provided under a Creative 00:00:02.400 --> 00:00:03.840 Commons license. 00:00:03.840 --> 00:00:06.850 Your support will help MIT OpenCourseWare continue to 00:00:06.850 --> 00:00:10.520 offer high-quality educational resources for free. 00:00:10.520 --> 00:00:13.390 To make a donation or view additional materials from 00:00:13.390 --> 00:00:17.490 hundreds of MIT courses, visit MIT OpenCourseWare at 00:00:17.490 --> 00:00:18.740 ocw.mit.edu. 00:00:21.020 --> 00:00:22.880 Tuesday will be the first weekly quiz, 00:00:22.880 --> 00:00:25.170 celebration that is. 00:00:25.170 --> 00:00:26.790 That will be at the beginning of recitation. 00:00:26.790 --> 00:00:28.620 You'll have 10 minutes. 00:00:28.620 --> 00:00:31.270 It'll be a short one-pager. 00:00:31.270 --> 00:00:33.170 You just write on the page. 00:00:33.170 --> 00:00:36.560 All you bring is your periodic table, which you should have 00:00:36.560 --> 00:00:38.250 gotten in recitation yesterday. 00:00:38.250 --> 00:00:42.190 Periodic Table, table of constants, calculator, 00:00:42.190 --> 00:00:47.000 something to write with, but no aid sheet on the weeklies. 00:00:47.000 --> 00:00:49.910 Readings: Readings, I urge you to read 00:00:49.910 --> 00:00:51.720 before you come to class. 00:00:51.720 --> 00:00:54.680 And so if you go to the website, you can go to 00:00:54.680 --> 00:00:57.560 Schedule, and in the schedule, you'll see stuff like this 00:00:57.560 --> 00:01:01.860 that tells you what the readings are for the day. 00:01:01.860 --> 00:01:04.640 As I mentioned last day, the lectures are being 00:01:04.640 --> 00:01:09.990 videographed and posted probably within an hour on the 00:01:09.990 --> 00:01:15.630 website and any of the images that I show are also recorded, 00:01:15.630 --> 00:01:18.150 burned as PDFs and uploaded. 00:01:18.150 --> 00:01:23.640 So you don't have to be put in high-speed stenographic mode 00:01:23.640 --> 00:01:27.160 in order to attend class. 00:01:27.160 --> 00:01:29.260 What's the other thing I wanted to tell you? 00:01:29.260 --> 00:01:32.340 If you're new to the class or if you need to change your 00:01:32.340 --> 00:01:36.820 recitation section because your conditions have changed, 00:01:36.820 --> 00:01:39.780 do not simply go to the other class. 00:01:39.780 --> 00:01:41.350 We're trying to regulate enrollment, 00:01:41.350 --> 00:01:42.680 particularly on Tuesdays. 00:01:42.680 --> 00:01:46.740 If the TA shows up expecting 20 students and has 20 copies 00:01:46.740 --> 00:01:49.950 of the quiz and 25 people show up, that's not 00:01:49.950 --> 00:01:51.240 a recipe for success. 00:01:51.240 --> 00:01:54.510 So you must go to my administrative assistant, 00:01:54.510 --> 00:01:57.300 Hilary Sheldon in order to change recitation. 00:01:57.300 --> 00:01:59.830 And if you need any of the handouts and so on, it's just 00:01:59.830 --> 00:02:04.740 down the hall here in Building 8, Room 201. 00:02:04.740 --> 00:02:06.720 I think that's all that I had to say. 00:02:06.720 --> 00:02:09.160 If you go here the videos are all listed. 00:02:09.160 --> 00:02:14.040 So last day we started talking about taxonomy and that led us 00:02:14.040 --> 00:02:16.270 to the beginnings of atomic theory. 00:02:16.270 --> 00:02:19.790 We visited with Democritus, 400 BC. 00:02:19.790 --> 00:02:22.790 We had that detour with the idiocy of Aristotle, and then 00:02:22.790 --> 00:02:26.510 eventually got back to our senses, and we saw John Dalton 00:02:26.510 --> 00:02:30.540 with his table of the elements, and then ultimately 00:02:30.540 --> 00:02:32.260 onto Mendeleyev. 00:02:32.260 --> 00:02:35.240 And I wanted to pick up the thread there. 00:02:35.240 --> 00:02:38.390 But before doing so, draw attention the fact that John 00:02:38.390 --> 00:02:42.900 Dalton did more than simply develop a set of fonts for us. 00:02:42.900 --> 00:02:46.090 So he proposed the model of the atom and this goes back 00:02:46.090 --> 00:02:50.440 little over 200 years ago, and these are the 00:02:50.440 --> 00:02:52.120 features of the model. 00:02:52.120 --> 00:02:54.680 First of all, that matter is composed of atoms that are 00:02:54.680 --> 00:02:56.360 indivisible and indestructible. 00:02:56.360 --> 00:02:57.560 So that goes all the way back to 00:02:57.560 --> 00:03:00.780 Democritus, nothing new there. 00:03:00.780 --> 00:03:02.685 All atoms of an element are identical. 00:03:05.240 --> 00:03:08.330 Atoms of different elements have different weights and 00:03:08.330 --> 00:03:09.550 different chemical properties. 00:03:09.550 --> 00:03:12.170 This is the emergence of modern material science, the 00:03:12.170 --> 00:03:15.410 connection between properties and elements. 00:03:15.410 --> 00:03:18.900 So the weight arguably is one of the properties, but the 00:03:18.900 --> 00:03:20.910 only way they could distinguish elements at that 00:03:20.910 --> 00:03:24.890 time was by their atomic mass. 00:03:24.890 --> 00:03:28.110 Atoms of different elements combine in simple whole-number 00:03:28.110 --> 00:03:30.600 ratios to form compounds. 00:03:30.600 --> 00:03:33.120 Well, that makes sense because they're the elements. 00:03:33.120 --> 00:03:34.750 They are the elemental building blocks. 00:03:34.750 --> 00:03:39.690 If I told you you could build a structure made of blocks and 00:03:39.690 --> 00:03:41.720 part-way through your construction I say, why don't 00:03:41.720 --> 00:03:44.210 you cut that block in half, you'd say, well, then the 00:03:44.210 --> 00:03:46.510 block isn't the building block. 00:03:46.510 --> 00:03:48.730 It's the half-block that's the building block. 00:03:48.730 --> 00:03:52.650 So axiomatically if these are the elements they must combine 00:03:52.650 --> 00:03:55.650 in simple whole-number ratios to form compounds. 00:03:55.650 --> 00:03:58.600 And lastly, atoms cannot be created or destroyed. 00:03:58.600 --> 00:04:01.180 Well, he wasn't foretelling E equals mc squared. 00:04:01.180 --> 00:04:03.700 What he was saying was that if you take elements and you 00:04:03.700 --> 00:04:06.620 combine them to form a compound, if you subsequently 00:04:06.620 --> 00:04:08.510 decompose the compound you get the elements 00:04:08.510 --> 00:04:10.690 back as they were. 00:04:10.690 --> 00:04:16.250 So those are the features of John Dalton's model. 00:04:16.250 --> 00:04:18.780 And we fast forward to 1869. 00:04:18.780 --> 00:04:22.520 And this is the knowledge that was available at the time in 00:04:22.520 --> 00:04:25.380 terms of the elements that had been isolated and 00:04:25.380 --> 00:04:26.500 characterized. 00:04:26.500 --> 00:04:28.220 And it was with this set of elements 00:04:28.220 --> 00:04:30.410 that Mendeleyev operated. 00:04:30.410 --> 00:04:34.250 On file cards, in his breast pocket, he carried with him 00:04:34.250 --> 00:04:35.150 everywhere. 00:04:35.150 --> 00:04:37.760 And he wrote down the names of the elements and their atomic 00:04:37.760 --> 00:04:42.620 masses and their properties and whatever else he could use 00:04:42.620 --> 00:04:44.510 the way of characterizing them. 00:04:44.510 --> 00:04:46.620 And during the course of writing a textbook-- 00:04:46.620 --> 00:04:50.250 he had just finished a chapter on the alkaline metals and he 00:04:50.250 --> 00:04:52.220 was sitting in the railway station playing 00:04:52.220 --> 00:04:53.780 solitaire, and boom! 00:04:53.780 --> 00:05:00.110 The flash came to him that you don't put arsenic underneath 00:05:00.110 --> 00:05:03.590 aluminum even though it's next in mass to zinc. You move it 00:05:03.590 --> 00:05:05.470 over and you don't even put it under silicon. 00:05:05.470 --> 00:05:06.840 You put it under phosphorus. 00:05:06.840 --> 00:05:09.680 And furthermore, what he said was there's going to be an 00:05:09.680 --> 00:05:13.780 element here discovered under silicon and it will have these 00:05:13.780 --> 00:05:14.410 properties. 00:05:14.410 --> 00:05:18.290 And let's look a little bit more deeply at the properties. 00:05:18.290 --> 00:05:23.870 But before doing so I want to say that by announcing this 00:05:23.870 --> 00:05:28.580 prediction of what the element should be that's missing is 00:05:28.580 --> 00:05:31.010 that we start to see the evolution of principles of 00:05:31.010 --> 00:05:31.930 modern chemistry. 00:05:31.930 --> 00:05:34.320 First of all, he recognized the pattern. 00:05:34.320 --> 00:05:36.060 So did Lothar Meyer in Tuebingen. 00:05:36.060 --> 00:05:39.090 So they both proposed a periodic table of the 00:05:39.090 --> 00:05:42.320 elements, but where Mendeleyev pulled away from the pack and 00:05:42.320 --> 00:05:44.250 distinguished himself was that he developed a 00:05:44.250 --> 00:05:45.880 quantitative model. 00:05:45.880 --> 00:05:48.000 And I haven't shown you the quantitative aspect yet. 00:05:48.000 --> 00:05:49.530 That's coming next. 00:05:49.530 --> 00:05:52.020 That explains the observations, and that's good. 00:05:52.020 --> 00:05:53.420 You might say, well, that's just curve 00:05:53.420 --> 00:05:54.880 fitting if you're a cynic. 00:05:54.880 --> 00:05:59.440 But it makes predictions that can be tested by experiment, 00:05:59.440 --> 00:06:01.360 tested by experiment. 00:06:01.360 --> 00:06:03.430 So let's take a look. 00:06:03.430 --> 00:06:06.950 He said that under silicon, but above tin, there would be 00:06:06.950 --> 00:06:07.420 an element. 00:06:07.420 --> 00:06:08.680 He called it eka-silicon. 00:06:08.680 --> 00:06:11.570 Eka is a Sanskrit word, which means one after. 00:06:11.570 --> 00:06:15.090 So this is the element one after silicon. 00:06:15.090 --> 00:06:19.610 It was eventually isolated and given the name germanium. 00:06:19.610 --> 00:06:21.770 Mendeleyev said it would have an atomic mass of 00:06:21.770 --> 00:06:23.200 72 grams per mole. 00:06:23.200 --> 00:06:25.640 In fact, it's 72.59. 00:06:25.640 --> 00:06:28.510 He said it would have a density of 5.5 grams per cubic 00:06:28.510 --> 00:06:29.060 centimeter. 00:06:29.060 --> 00:06:30.870 It's 5.36. 00:06:30.870 --> 00:06:33.462 This is 1869. 00:06:33.462 --> 00:06:35.940 He said that it would have a high melting point, whatever 00:06:35.940 --> 00:06:39.520 that means, and it melts at 958 Celsius. 00:06:39.520 --> 00:06:40.430 It's compounds. 00:06:40.430 --> 00:06:43.750 he said it would form a dioxide with a high melting 00:06:43.750 --> 00:06:45.660 point and a density of 4.7. 00:06:45.660 --> 00:06:49.590 It forms a dioxide and its density is 4.70. 00:06:49.590 --> 00:06:53.430 In fact, there's a story about a French mineralogist who came 00:06:53.430 --> 00:06:57.050 upon some of the stuff that ultimately became germanium 00:06:57.050 --> 00:07:01.200 dioxide, measured its density and reported it to Mendeleyev 00:07:01.200 --> 00:07:03.750 in a letter, saying, you know I measured the stuff and it's 00:07:03.750 --> 00:07:05.880 5.3 grams per cubic centimeter. 00:07:05.880 --> 00:07:07.960 Mendeleyev wrote him back and he said, make 00:07:07.960 --> 00:07:08.780 the measurement again. 00:07:08.780 --> 00:07:09.630 You're wrong. 00:07:09.630 --> 00:07:11.770 He wrote back three months later and said, 00:07:11.770 --> 00:07:12.870 I measured it again. 00:07:12.870 --> 00:07:14.620 It's 4.7. 00:07:14.620 --> 00:07:17.055 That was the genius of Mendeleyev. 00:07:17.055 --> 00:07:20.330 To go way out on a limb and make those predictions. 00:07:20.330 --> 00:07:23.960 And so I've made the case for the table of the elements. 00:07:23.960 --> 00:07:25.910 Why do we call it the Periodic Table? 00:07:25.910 --> 00:07:27.310 What's the periodic about? 00:07:27.310 --> 00:07:28.490 Well, the periodic-- 00:07:28.490 --> 00:07:31.430 take a look here, if you go to the website there's a tab 00:07:31.430 --> 00:07:35.040 called Courseware and there's a tab called Periodic Table. 00:07:35.040 --> 00:07:39.450 And you can go to the Periodic Table and ask the software to 00:07:39.450 --> 00:07:40.810 plot property. 00:07:40.810 --> 00:07:44.470 So for example this is boiling point versus proton number or 00:07:44.470 --> 00:07:45.690 atomic number. 00:07:45.690 --> 00:07:48.630 And so you see the boiling point varies as you move from 00:07:48.630 --> 00:07:50.630 low atomic number to high atomic number. 00:07:50.630 --> 00:07:52.110 But it's not totally random. 00:07:52.110 --> 00:07:54.290 It's not a Gaussian distribution. 00:07:54.290 --> 00:07:55.280 There are features. 00:07:55.280 --> 00:07:58.410 It goes up and down, up, down, up and down. 00:07:58.410 --> 00:08:01.180 If you train your eye a little bit you'll actually see some 00:08:01.180 --> 00:08:03.350 regularity, a pattern there. 00:08:03.350 --> 00:08:04.380 Maybe that's not so good. 00:08:04.380 --> 00:08:05.100 Let's look at this one. 00:08:05.100 --> 00:08:06.620 This is electrical conductivity. 00:08:06.620 --> 00:08:10.680 And again, up, down, up, down and look at those red lines. 00:08:10.680 --> 00:08:11.880 There, there, there, there. 00:08:11.880 --> 00:08:12.760 Don't you see something? 00:08:12.760 --> 00:08:14.020 That's a pattern. 00:08:14.020 --> 00:08:16.690 And they're almost equally spaced. 00:08:16.690 --> 00:08:20.720 So that was where Mendeleyev announced his Periodic Law, 00:08:20.720 --> 00:08:24.520 where he said the properties are related to the identity of 00:08:24.520 --> 00:08:29.930 the atoms. And furthermore, he announced, that the properties 00:08:29.930 --> 00:08:33.870 are a periodic variation in atomic mass. 00:08:33.870 --> 00:08:44.320 So let's get that now Mendeleyev's Periodic Law, and 00:08:44.320 --> 00:08:57.220 the properties of the elements vary 00:08:57.220 --> 00:09:04.960 periodically with atomic mass. 00:09:08.040 --> 00:09:09.290 That was Mendeleyev. 00:09:10.940 --> 00:09:17.010 So now that we know that we can go forward, and here's now 00:09:17.010 --> 00:09:21.010 the full-blown Periodic Table according to the framework 00:09:21.010 --> 00:09:22.250 that Mendeleyev established. 00:09:22.250 --> 00:09:24.520 Now if you look at this carefully, you'll see down 00:09:24.520 --> 00:09:27.600 here things get whited out and there's these strange 00:09:27.600 --> 00:09:30.000 notations, uu, m, and all that stuff. 00:09:30.000 --> 00:09:30.730 What's that all about? 00:09:30.730 --> 00:09:32.210 This is where the super heavies lie. 00:09:32.210 --> 00:09:34.190 These are all synthetic elements. 00:09:34.190 --> 00:09:39.820 Transuranic, they're made by high-energy reactions, 00:09:39.820 --> 00:09:44.250 so-called high-energy physics in what you might call 00:09:44.250 --> 00:09:48.020 accelerators, atom smashers, what have you. 00:09:48.020 --> 00:09:51.360 And there's only three places on the planet where you can 00:09:51.360 --> 00:09:54.340 conduct such reactions. 00:09:54.340 --> 00:09:59.510 One of them is in Darmstadt in Germany. 00:09:59.510 --> 00:10:02.860 One is in Dubna, just outside of Moscow. 00:10:02.860 --> 00:10:04.860 And if you want to stay home-- 00:10:04.860 --> 00:10:07.390 and eschew the frequent flyer miles-- you can go to 00:10:07.390 --> 00:10:08.550 Berkeley, California. 00:10:08.550 --> 00:10:11.690 These are the three places where we have the accelerators 00:10:11.690 --> 00:10:17.110 capable of making such compounds. 00:10:17.110 --> 00:10:22.210 And so, take a look carefully at what the nomenclature is. 00:10:22.210 --> 00:10:26.690 The way you name them is by using these Latin ordinals. 00:10:26.690 --> 00:10:29.420 So un, bi, tri, quad and so on. 00:10:29.420 --> 00:10:33.760 So if you wanted to name element 115, it's ununpentium. 00:10:33.760 --> 00:10:36.880 You want the ium ending. 00:10:36.880 --> 00:10:37.900 And you can make these up. 00:10:37.900 --> 00:10:40.730 You could make up element 205 if you want to or whatever. 00:10:40.730 --> 00:10:44.540 My favorite is 111 because that's unununium. 00:10:44.540 --> 00:10:49.760 But there they are, so you can have fun with those. 00:10:49.760 --> 00:10:55.870 But with time, the elements are being named and these have 00:10:55.870 --> 00:10:58.420 been synthesized since your version of 00:10:58.420 --> 00:11:00.080 the table was printed. 00:11:00.080 --> 00:11:05.080 And so number 110 is named Darmstadtium in honor of the 00:11:05.080 --> 00:11:07.820 team at Darmstadt that first isolated it. 00:11:07.820 --> 00:11:13.570 And number 111 was just named two years ago and the name is 00:11:13.570 --> 00:11:15.250 roentgenium after Wilhelm Roentgen, 00:11:15.250 --> 00:11:18.500 who discovered x-rays. 00:11:18.500 --> 00:11:19.940 Now what is it about discovery? 00:11:19.940 --> 00:11:26.060 Well, here's an example of one such reaction that would give 00:11:26.060 --> 00:11:27.650 you an element. 00:11:27.650 --> 00:11:31.550 So if we had access to one of these devices we could take, 00:11:31.550 --> 00:11:35.790 for example, lead and nickel and accelerate them to very, 00:11:35.790 --> 00:11:39.740 very high energies. 00:11:39.740 --> 00:11:42.790 And then we could make 110, ununilium. 00:11:42.790 --> 00:11:49.010 Or now we'll call it Darmstadtium plus neutron. 00:11:49.010 --> 00:11:54.170 And in doing so we've generated the new element. 00:11:54.170 --> 00:11:58.650 But we can't just say we've made the element and publish. 00:11:58.650 --> 00:12:01.470 We have to be able to characterize it. 00:12:01.470 --> 00:12:05.910 Remember the reason that we gave Cavendish the credit for 00:12:05.910 --> 00:12:08.590 discovering hydrogen wasn't that he's the first to know 00:12:08.590 --> 00:12:11.970 that hydrogen exists, but he isolated it and gave it value. 00:12:11.970 --> 00:12:14.120 So if you look at the rest of the periodic table, you get 00:12:14.120 --> 00:12:17.630 things like boiling point, melting point, density, 00:12:17.630 --> 00:12:20.070 electronegativity, first ionization energy. 00:12:20.070 --> 00:12:21.650 There's a lot of information there. 00:12:21.650 --> 00:12:23.000 If you go down here there's nothing. 00:12:23.000 --> 00:12:24.390 It's all blanks. 00:12:24.390 --> 00:12:27.810 These things have very, very short lifetimes. 00:12:27.810 --> 00:12:29.230 Fractions of a second. 00:12:29.230 --> 00:12:30.530 But you have to isolate them. 00:12:30.530 --> 00:12:32.930 There's certain criteria before you can publish. 00:12:32.930 --> 00:12:35.820 And all this is regulated by this governing body called the 00:12:35.820 --> 00:12:38.930 International Union of Pure and Applied Chemistry, So 00:12:38.930 --> 00:12:44.530 UPAC, the organization that finally rules on the 00:12:44.530 --> 00:12:46.240 legitimacy of any of these. 00:12:46.240 --> 00:12:48.450 And actually there have been some retractions in recent 00:12:48.450 --> 00:12:50.790 years, where people published claiming-- 00:12:50.790 --> 00:12:53.870 I think there was a report out of Berkeley claiming that 00:12:53.870 --> 00:12:57.170 they'd synthesized 115 and then subsequently that was 00:12:57.170 --> 00:13:01.060 retracted because they couldn't support the property 00:13:01.060 --> 00:13:02.870 measurements 00:13:02.870 --> 00:13:06.570 Last thing is, if you're interested, want to do some 00:13:06.570 --> 00:13:09.150 extra reading, there's a fantastic book about 00:13:09.150 --> 00:13:09.690 Mendeleyev. 00:13:09.690 --> 00:13:13.630 He was the youngest of 14 children, came out of a very 00:13:13.630 --> 00:13:18.380 poor family in Siberia and rose to be a giant of his day. 00:13:18.380 --> 00:13:20.490 He was a polymath. 00:13:20.490 --> 00:13:23.910 He, among some of the other things he did, he worked for 00:13:23.910 --> 00:13:28.485 the Ministry of Weights and Measures under the czar. 00:13:31.480 --> 00:13:35.270 The czar was interested in taxation of alcohol. 00:13:35.270 --> 00:13:41.150 And if you mix equal volumes of water and vodka you don't 00:13:41.150 --> 00:13:42.420 get additivity. 00:13:42.420 --> 00:13:46.460 So 100 mL of water plus 100 mL of vodka doesn't give 200 mL. 00:13:46.460 --> 00:13:47.680 It gives less. 00:13:47.680 --> 00:13:52.000 And so Mendeleyev did a study to determine what the optimum 00:13:52.000 --> 00:13:55.280 ratio is so that people couldn't misrepresent the 00:13:55.280 --> 00:13:58.340 amount of alcohol in the beverage. 00:13:58.340 --> 00:14:01.820 And set the standard at 40% alcohol by volume, which is 00:14:01.820 --> 00:14:03.700 used the world over to this day. 00:14:03.700 --> 00:14:08.170 He also came to the United States in 1876 to go to 00:14:08.170 --> 00:14:10.060 Titusville, Pennsylvania, where the first 00:14:10.060 --> 00:14:11.550 oil well was drilled. 00:14:11.550 --> 00:14:15.790 And did an exhaustive study of what was the American 00:14:15.790 --> 00:14:17.140 petroleum industry at the time. 00:14:17.140 --> 00:14:19.880 And then went back to Imperial Russia and did the same survey 00:14:19.880 --> 00:14:23.660 for the Czar in Imperial Russia, including a report 00:14:23.660 --> 00:14:26.370 that recommended how to develop the natural resources 00:14:26.370 --> 00:14:27.890 of the time. 00:14:27.890 --> 00:14:29.035 He was really an amazing man. 00:14:29.035 --> 00:14:31.100 He wrote text books and so on. 00:14:31.100 --> 00:14:34.730 And nobody in science-- 00:14:34.730 --> 00:14:36.890 I would venture to say-- has not heard of 00:14:36.890 --> 00:14:38.270 the periodic table. 00:14:38.270 --> 00:14:40.010 Mendeleyev died in 1906. 00:14:40.010 --> 00:14:42.760 The Nobel Prizes were first offered in 1901. 00:14:42.760 --> 00:14:48.560 So there were five years where he was close to the top for 00:14:48.560 --> 00:14:52.110 winning the Noble Prize but was eked out by somebody else. 00:14:52.110 --> 00:14:53.630 When you look back at those other Nobel 00:14:53.630 --> 00:14:55.450 Prizes, they were deserved. 00:14:55.450 --> 00:14:59.170 But none more so than that for Mendeleyev. 00:14:59.170 --> 00:15:04.420 So ironically the man who gave us seminal knowledge of all 00:15:04.420 --> 00:15:07.780 chemistry was never awarded the Nobel Prize. 00:15:07.780 --> 00:15:11.000 And there's probably a lot of politics in there. 00:15:11.000 --> 00:15:14.120 And as I said last day, here's the typical picture of him. 00:15:14.120 --> 00:15:16.280 In this he sort of looks like a street person, 00:15:16.280 --> 00:15:18.590 disheveled and so on. 00:15:18.590 --> 00:15:21.780 But this was the man that gave us the periodic table. 00:15:21.780 --> 00:15:26.580 That's him at age 35 when he annunciated the Periodic Law. 00:15:26.580 --> 00:15:28.680 So good for him. 00:15:28.680 --> 00:15:29.160 Alright. 00:15:29.160 --> 00:15:34.720 So now, let's take a look a little deeper about the 00:15:34.720 --> 00:15:36.070 properties of the elements. 00:15:36.070 --> 00:15:38.070 How do we understand the properties of the elements? 00:15:38.070 --> 00:15:39.820 For the properties elements we're going to have to look 00:15:39.820 --> 00:15:41.380 inside the atom. 00:15:41.380 --> 00:15:43.120 If you did your reading you undoubtedly 00:15:43.120 --> 00:15:44.790 came across this table. 00:15:44.790 --> 00:15:48.000 Which at first pass, deconstructs the atom into 00:15:48.000 --> 00:15:50.100 three simple particles: the electron, the 00:15:50.100 --> 00:15:51.690 proton and the neutron. 00:15:51.690 --> 00:15:54.220 Here are their symbols, e, p and n. 00:15:54.220 --> 00:15:58.080 And they're distinguished by charge and mass. 00:15:58.080 --> 00:16:02.030 So the electron has charge, minus 1.6 times 10 to the 00:16:02.030 --> 00:16:04.130 minus 19 Coulombs. 00:16:04.130 --> 00:16:07.940 And a very low mass: 9.11 times 10 to the minus 31 00:16:07.940 --> 00:16:11.360 kilograms. The electronic charge is balanced by the 00:16:11.360 --> 00:16:12.590 protonic charge. 00:16:12.590 --> 00:16:14.260 The atom is net neutral. 00:16:14.260 --> 00:16:18.060 So the proton has a charge of plus 1.6 times 10 to the minus 00:16:18.060 --> 00:16:19.540 19 Coulombs. 00:16:19.540 --> 00:16:22.920 The neutron, as the name implies, has 0 charge. 00:16:22.920 --> 00:16:25.350 The proton and the neutron have very nearly 00:16:25.350 --> 00:16:27.170 equal masses, however. 00:16:27.170 --> 00:16:27.530 Right. 00:16:27.530 --> 00:16:30.390 And just a word about the units. 00:16:30.390 --> 00:16:35.440 The units here are given in terms of the Systeme 00:16:35.440 --> 00:16:36.640 Internationale. 00:16:36.640 --> 00:16:40.140 So when we use the term, C, capital C is for the Coulomb. 00:16:43.230 --> 00:16:45.240 And that's the unit of charge. 00:16:45.240 --> 00:16:48.810 And it has an uppercase letter because it's named after a 00:16:48.810 --> 00:16:52.260 scientist. In this case, the French scientist, Coulomb, 00:16:52.260 --> 00:16:55.120 whereas the gram is not named after a 00:16:55.120 --> 00:16:57.790 scientist and so it's lowercase. 00:16:57.790 --> 00:17:00.210 And then we can amplify by powers of three. 00:17:00.210 --> 00:17:03.620 So if I want 1,000 of these, I put a lowercase k here. 00:17:03.620 --> 00:17:07.150 If I put an uppercase K, I end up with the unit Kelvin, which 00:17:07.150 --> 00:17:10.180 is the unit of temperature named after Lord Kelvin. 00:17:10.180 --> 00:17:14.880 And all of this is known as SI units, which is the 00:17:14.880 --> 00:17:16.100 International System. 00:17:16.100 --> 00:17:19.510 And it's not because the scientists don't know how to 00:17:19.510 --> 00:17:20.970 develop an abbreviation. 00:17:20.970 --> 00:17:23.720 This was originally developed when French was the 00:17:23.720 --> 00:17:26.180 international language of science. 00:17:26.180 --> 00:17:31.000 So this is known as the Systeme Internationale and all 00:17:31.000 --> 00:17:32.970 of these units were defined at that time. 00:17:32.970 --> 00:17:40.760 And the term SI sticks that's the legacy. 00:17:40.760 --> 00:17:43.810 All right, so now if we go to the Periodic Table. 00:17:43.810 --> 00:17:48.400 When we start looking at the elements, we can look at any 00:17:48.400 --> 00:17:51.340 entry on the Periodic Table, and we have the chemical 00:17:51.340 --> 00:18:00.260 symbol that I'm designating here as uppercase X, and this 00:18:00.260 --> 00:18:02.620 was originally John Dalton with the I and the 00:18:02.620 --> 00:18:03.890 circle around it. 00:18:03.890 --> 00:18:09.520 And about 30 years later the Swedish scientist Berzelius 00:18:09.520 --> 00:18:13.030 suggested that we use neutral units and so therefore we have 00:18:13.030 --> 00:18:16.920 the Latin coming in for many of the elements, such as iron, 00:18:16.920 --> 00:18:19.970 Fe, ferrum, and gold Au, aurum. 00:18:19.970 --> 00:18:23.430 In the upper-left corner, we have the quality I'm 00:18:23.430 --> 00:18:29.780 representing here, A And A is the mass number. 00:18:29.780 --> 00:18:31.960 Some people call it the atomic weight. 00:18:31.960 --> 00:18:34.470 And it is the sum of the masses of all the 00:18:34.470 --> 00:18:35.350 constituents. 00:18:35.350 --> 00:18:39.210 So it's the sum of the mass of the protons, so it's the 00:18:39.210 --> 00:18:43.360 proton number plus the neutron number plus 00:18:43.360 --> 00:18:44.390 the electron number. 00:18:44.390 --> 00:18:48.330 But since the electron weighs 1/1800 of what these others 00:18:48.330 --> 00:18:50.450 weigh, you normally don't consider this. 00:18:50.450 --> 00:18:51.240 It doesn't matter. 00:18:51.240 --> 00:18:55.870 So just adding protons plus neutrons gets you to what we 00:18:55.870 --> 00:18:57.290 call the atomic weight. 00:18:57.290 --> 00:19:02.420 And then down in the lower left corner we have Z and Z is 00:19:02.420 --> 00:19:03.850 the proton number. 00:19:09.070 --> 00:19:13.250 And as the name implies, it's equal to the number of protons 00:19:13.250 --> 00:19:20.200 in the nucleus, which then equals the number of electrons 00:19:20.200 --> 00:19:23.430 outside the nucleus in the neutral atom. 00:19:25.990 --> 00:19:30.360 Now I'm specifying neutral atom, because it's not 00:19:30.360 --> 00:19:32.820 necessary for atoms to be neutral and we'll take a look 00:19:32.820 --> 00:19:36.040 at those in a moment. 00:19:36.040 --> 00:19:37.690 A point about redundancy here. 00:19:37.690 --> 00:19:40.930 We don't really need the proton number and the chemical 00:19:40.930 --> 00:19:44.840 symbol because the proton number really defines. 00:19:44.840 --> 00:19:47.110 The proton number is like the Social Security number. 00:19:47.110 --> 00:19:53.820 This is the identity number of the atom. 00:19:53.820 --> 00:19:55.180 If we change the the proton number, 00:19:55.180 --> 00:19:58.200 we change its identity. 00:19:58.200 --> 00:20:01.360 So for example, I could write sodium. 00:20:01.360 --> 00:20:04.940 Sodium 23 and 11. 00:20:04.940 --> 00:20:06.220 I don't need the 11. 00:20:06.220 --> 00:20:09.410 11 means it's sodium or sodium means it's 11. 00:20:09.410 --> 00:20:13.080 So I could just write this as 23 sodium. 00:20:13.080 --> 00:20:15.860 So I know it's sodium, that means it's got 11 protons and 00:20:15.860 --> 00:20:18.220 23 minus 11 must be neutrons. 00:20:18.220 --> 00:20:20.050 Or if I wanted to be a smart aleck, I could 00:20:20.050 --> 00:20:22.030 write this : 23 11. 00:20:22.030 --> 00:20:22.880 That's sodium. 00:20:22.880 --> 00:20:25.640 I don't need to put anything here. 00:20:25.640 --> 00:20:29.850 But there's no smart alecks here, of course. 00:20:29.850 --> 00:20:34.980 So for example, we could then show this reaction as-- 00:20:34.980 --> 00:20:36.010 this is what? 00:20:36.010 --> 00:20:37.520 208. 00:20:37.520 --> 00:20:39.720 This is lead, 208. 00:20:39.720 --> 00:20:49.050 And nickel, 62 gives us Darmstadtium with a value of 00:20:49.050 --> 00:20:51.900 269 and the neutron is 1. 00:20:51.900 --> 00:20:56.450 You can see how these reactions can be made to go. 00:20:56.450 --> 00:21:01.130 Now atoms don't necessarily have to be net neutral. 00:21:01.130 --> 00:21:07.950 We can have something that is net non-zero charge. 00:21:07.950 --> 00:21:14.270 Net non-zero charge on the atom gives it the term, ion. 00:21:14.270 --> 00:21:17.740 Ion is an atom with net non-zero charge. 00:21:17.740 --> 00:21:22.810 And we have two cases where the atom is net positive. 00:21:22.810 --> 00:21:26.110 If the atom is net positive that's the result of electron 00:21:26.110 --> 00:21:27.780 deficiency. 00:21:27.780 --> 00:21:29.420 The atom is electron deficient. 00:21:32.020 --> 00:21:35.510 And we term such an atom the cation. 00:21:35.510 --> 00:21:36.750 There's two types of ions. 00:21:36.750 --> 00:21:38.100 The cation. 00:21:38.100 --> 00:21:41.740 And then we have something that is net negative. 00:21:41.740 --> 00:21:44.280 If it's net negative, it means it's electron-rich. 00:21:44.280 --> 00:21:48.660 That is to say, there are more electrons than protons and the 00:21:48.660 --> 00:21:52.370 net negative ion is called the anion. 00:21:52.370 --> 00:21:53.910 And you can try to figure out ways. 00:21:53.910 --> 00:21:57.120 I sometimes think that cation has a t, which looks a little 00:21:57.120 --> 00:21:59.420 bit like a plus sign. 00:21:59.420 --> 00:22:03.960 Anion has five letters, minus has five letters. 00:22:03.960 --> 00:22:06.980 And they both end in n, but this has an n, which is 00:22:06.980 --> 00:22:07.700 negative or something. 00:22:07.700 --> 00:22:08.950 You'll figure something out. 00:22:13.210 --> 00:22:16.420 Now we've talked about varying charge at 00:22:16.420 --> 00:22:19.300 constant proton number. 00:22:19.300 --> 00:22:21.750 But the other thing we can do is we can look at-- 00:22:21.750 --> 00:22:27.640 you can vary the neutron number. 00:22:27.640 --> 00:22:30.050 Since the neutron has no charge you can vary the 00:22:30.050 --> 00:22:32.350 neutron number and not harm the identity and still have a 00:22:32.350 --> 00:22:32.980 neutral atom. 00:22:32.980 --> 00:22:41.690 So vary neutron number at constant proton number. 00:22:41.690 --> 00:22:45.030 And let's see what that is. 00:22:45.030 --> 00:22:48.220 That gives you something that looks like this. 00:22:48.220 --> 00:22:52.480 So for example, if you if you look at carbon, the atomic 00:22:52.480 --> 00:22:56.100 mass that's shown here is 12.011. 00:22:56.100 --> 00:22:58.550 And you'd say, well, gee, if it's got 6 neutrons and 6 00:22:58.550 --> 00:23:01.130 protons, why isn't that 12 exactly? 00:23:01.130 --> 00:23:03.640 Well, this is the answer here. 00:23:03.640 --> 00:23:05.840 You can vary the neutron number at 00:23:05.840 --> 00:23:07.160 constant proton number. 00:23:07.160 --> 00:23:11.101 So let's take a look at how that plays out. 00:23:11.101 --> 00:23:14.660 The way that plays out is as following. 00:23:14.660 --> 00:23:16.930 Let's see I'm going to make a little table here. 00:23:24.580 --> 00:23:29.130 So we'll start with carbon 12. 00:23:29.130 --> 00:23:31.290 Carbon 12, so that means-- 00:23:31.290 --> 00:23:32.035 now I know what I'm going to do. 00:23:32.035 --> 00:23:37.820 I'm going to bring this down and make some headings for me. 00:23:37.820 --> 00:23:40.230 This will be my proton number and this will 00:23:40.230 --> 00:23:43.230 be my neutron number. 00:23:43.230 --> 00:23:45.180 And finally I'm going to talk about 00:23:45.180 --> 00:23:46.990 abundance, natural abundance. 00:23:49.560 --> 00:23:54.260 So carbon 12, since it's carbon, axiomatically it must 00:23:54.260 --> 00:23:55.850 have 6 protons. 00:23:55.850 --> 00:23:59.170 And 12 minus 6 is 6, so it's got 6 neutrons. 00:23:59.170 --> 00:24:02.260 And this is the dominant form of carbon. 00:24:02.260 --> 00:24:05.370 If you took a chemical analysis of the carbon you'd 00:24:05.370 --> 00:24:12.660 find that over 98%, 98.892% of the carbon atoms that you 00:24:12.660 --> 00:24:18.820 examined would be of this form, carbon 12. 00:24:18.820 --> 00:24:22.980 Now there's also carbon 13. 00:24:22.980 --> 00:24:25.660 Has to be 6, otherwise it's not carbon. 00:24:25.660 --> 00:24:27.690 That means it's got 7 neutrons. 00:24:27.690 --> 00:24:29.110 And it's a minority species. 00:24:29.110 --> 00:24:31.530 1.108%. 00:24:31.530 --> 00:24:34.490 And then there's a third form of carbon and 00:24:34.490 --> 00:24:36.310 that's carbon 14. 00:24:36.310 --> 00:24:40.870 Again, has to be 6 and it's got 8 neutrons. 00:24:40.870 --> 00:24:44.480 And it's found in vanishingly small quantities, one part in 00:24:44.480 --> 00:24:45.900 10 to the 12. 00:24:45.900 --> 00:24:50.710 Or we could call it ppt, parts per trillion. 00:24:50.710 --> 00:24:58.010 So this is same atomic number, same proton number, same Z but 00:24:58.010 --> 00:25:03.770 different mass numbers. 00:25:03.770 --> 00:25:04.960 Different A's. 00:25:04.960 --> 00:25:09.290 So all of these variants of carbon are found on the same 00:25:09.290 --> 00:25:12.120 place, the same spot on the Periodic Table. 00:25:12.120 --> 00:25:15.290 The Greek word for same is iso, and the word for place is 00:25:15.290 --> 00:25:18.370 topo, so these are called isotopes. 00:25:18.370 --> 00:25:22.970 The isotopes of carbon are species that have identical 00:25:22.970 --> 00:25:26.840 proton number but different neutron number. 00:25:26.840 --> 00:25:28.370 How about the units? 00:25:28.370 --> 00:25:29.650 What are the units here? 00:25:29.650 --> 00:25:32.620 Well, we have to give some kind of unit. 00:25:32.620 --> 00:25:36.790 I've been sort of freely going around and counting protons as 00:25:36.790 --> 00:25:37.740 one and so on. 00:25:37.740 --> 00:25:39.440 And here's the standard. 00:25:39.440 --> 00:25:48.330 The standard for mass is defined, and the definition 00:25:48.330 --> 00:25:49.720 goes like this. 00:25:49.720 --> 00:25:53.220 If you take carbon 12, which we just introduced to you, and 00:25:53.220 --> 00:25:58.580 we say that we're going to specify a mass of 12.000 grams 00:25:58.580 --> 00:26:05.400 exactly for a specified quantity, in other words, a 00:26:05.400 --> 00:26:08.850 specified number of these atoms. We have to say we'll 00:26:08.850 --> 00:26:13.550 take a certain number of these carbon atoms and specify the 00:26:13.550 --> 00:26:16.350 mass of that number is 12 exactly. 00:26:16.350 --> 00:26:23.680 And specified number of atoms being the mole. 00:26:23.680 --> 00:26:25.180 The mole. 00:26:25.180 --> 00:26:29.880 And it turns out that the mole has a value of 6.02 times 10 00:26:29.880 --> 00:26:30.900 to the 23rd. 00:26:30.900 --> 00:26:33.210 How do they get that number? 00:26:33.210 --> 00:26:37.300 A little bit more in the way of definitions. 00:26:37.300 --> 00:26:39.590 It was a concept put forth by a professor. 00:26:39.590 --> 00:26:41.660 So we're going to take some time on it because we respect 00:26:41.660 --> 00:26:45.870 professors, in this class at least. And so this was a 00:26:45.870 --> 00:26:51.400 concept put forth by Professor Amadeo Avogadro. 00:26:51.400 --> 00:26:55.580 Professor Avogadro, who was a professor of physics at the 00:26:55.580 --> 00:27:00.790 University of Turin, Torino. 00:27:00.790 --> 00:27:02.651 And he was a contemporary of John Dalton's and they were 00:27:02.651 --> 00:27:04.510 both studying gases. 00:27:04.510 --> 00:27:08.560 And it was Avogadro who taught us that, when you keep the 00:27:08.560 --> 00:27:11.860 pressure constant equal volumes of different gases 00:27:11.860 --> 00:27:14.250 contain equal numbers of molecules. 00:27:14.250 --> 00:27:17.980 It doesn't matter if you have argon, which is by itself 00:27:17.980 --> 00:27:21.180 atomic, or we have oxygen, which is diatomic, or you have 00:27:21.180 --> 00:27:25.360 methane, which is CH4, five atoms making a compound. 00:27:25.360 --> 00:27:27.740 Equal pressure, equal volume, equal 00:27:27.740 --> 00:27:29.270 numbers of those species. 00:27:29.270 --> 00:27:31.720 So that was Avogadro's Law. 00:27:31.720 --> 00:27:33.010 So let's put that down. 00:27:33.010 --> 00:27:46.160 At constant pressure equal volumes of different gases, 00:27:46.160 --> 00:27:51.340 contain identical numbers of atoms. Equal volumes of 00:27:51.340 --> 00:28:03.010 different gases contain equal numbers of molecules. 00:28:03.010 --> 00:28:06.280 And here I'm using the term molecule as a counting unit. 00:28:06.280 --> 00:28:08.690 So it could be, strictly speaking, an atom or it could 00:28:08.690 --> 00:28:10.800 be diatomic and so on. 00:28:10.800 --> 00:28:11.500 That's what it was. 00:28:11.500 --> 00:28:18.710 And out of honor for Avogadro, we name the number of atoms in 00:28:18.710 --> 00:28:20.950 the mole the Avogadro number. 00:28:20.950 --> 00:28:25.530 Which I've written 6.02 times 10 to the 23rd. 00:28:25.530 --> 00:28:28.220 Now how do we determine Avogadro's number? 00:28:28.220 --> 00:28:30.110 That's an interesting story. 00:28:30.110 --> 00:28:34.300 So first of all, we need two pieces of information. 00:28:34.300 --> 00:28:37.440 Because we're going to do this by the noblest form of 00:28:37.440 --> 00:28:39.480 chemistry, electrochemistry. 00:28:39.480 --> 00:28:42.210 So the first thing we're going to do is we're going to look 00:28:42.210 --> 00:28:49.090 at the work Michael Faraday in England. 00:28:49.090 --> 00:28:51.190 And what Michael Faraday did is he studied the 00:28:51.190 --> 00:28:53.200 electrodeposition of metal. 00:28:53.200 --> 00:28:57.470 And specifically he passed current through a cell and he 00:28:57.470 --> 00:28:59.850 electrodeposited silver. 00:28:59.850 --> 00:29:04.210 So he starts with silver plus, that's silver a cation, and by 00:29:04.210 --> 00:29:08.000 the action of electric current attaches an electron to silver 00:29:08.000 --> 00:29:09.790 and renders it neutral. 00:29:09.790 --> 00:29:14.820 Silver, which now plates out onto an electrode and they 00:29:14.820 --> 00:29:17.160 measured the mass. 00:29:17.160 --> 00:29:21.400 They measured the mass of silver-plated and they compare 00:29:21.400 --> 00:29:26.490 it to the amount of charge that was passed. 00:29:26.490 --> 00:29:27.740 They measured the charge. 00:29:30.430 --> 00:29:33.260 And you can get charge, because you know current. 00:29:33.260 --> 00:29:35.990 So charge is simply equal to the integral of the current 00:29:35.990 --> 00:29:36.830 times the time. 00:29:36.830 --> 00:29:38.560 You know the current, that's easy. 00:29:38.560 --> 00:29:47.030 And what Faraday found was that to make what we now know 00:29:47.030 --> 00:29:51.940 to be 108 grams of silver, 108 grams of silver, which we're 00:29:51.940 --> 00:29:55.010 going to subsequently recognize as the mole, which 00:29:55.010 --> 00:29:58.600 is identical to the amount, the number of particles in 108 00:29:58.600 --> 00:30:02.410 grams of silver, is equal to the number of particles in 12 00:30:02.410 --> 00:30:04.770 grams of carbon. 00:30:04.770 --> 00:30:08.690 Sort of an Avogadro-type harkening. 00:30:08.690 --> 00:30:10.330 He found that that is-- 00:30:10.330 --> 00:30:15.990 the equivalent requires 96,485 Coulombs. 00:30:15.990 --> 00:30:20.230 So you can say 1 mole of electrons gives me 1 mole of 00:30:20.230 --> 00:30:24.360 silver, so that's the charge on 1 mole of electrons, where 00:30:24.360 --> 00:30:28.210 Coulomb is the elementary charge, because we know 1 00:30:28.210 --> 00:30:35.390 electron per 1 silver atom deposited. 00:30:35.390 --> 00:30:38.620 So now if I know that's a mole of electrons, I need to find a 00:30:38.620 --> 00:30:41.270 charge on one electron, divide through and I get 00:30:41.270 --> 00:30:42.760 the Avogadro number. 00:30:42.760 --> 00:30:46.720 And to finish the story we have to wait about 50 years 00:30:46.720 --> 00:30:50.550 and come to the United States, where it's Robert Millikan, 00:30:50.550 --> 00:30:54.170 Robert Millikan at the University of Chicago doing 00:30:54.170 --> 00:30:58.130 the oil drop experiment through which we learn the 00:30:58.130 --> 00:30:59.540 elementary charge. 00:30:59.540 --> 00:31:02.550 And here's the cartoon of the oil drop experiment. 00:31:02.550 --> 00:31:04.085 I took this from a different text. 00:31:04.085 --> 00:31:05.940 It's not shown in your text. 00:31:05.940 --> 00:31:10.340 So I actually did this experiment as a sophomore at 00:31:10.340 --> 00:31:11.200 the University of Toronto. 00:31:11.200 --> 00:31:13.410 They had us repeat some of the great experiments of physics, 00:31:13.410 --> 00:31:14.700 the ones that were accessible, obviously. 00:31:14.700 --> 00:31:18.450 I couldn't do high-energy physics in an afternoon. 00:31:18.450 --> 00:31:20.350 That would have taken me a little bit longer. 00:31:20.350 --> 00:31:21.680 But we did this one. 00:31:21.680 --> 00:31:25.010 And so it consists of an atomizer, sort of a perfume 00:31:25.010 --> 00:31:28.360 atomizer, in which there's oil. 00:31:28.360 --> 00:31:33.000 And by the action of atomization we form a shower 00:31:33.000 --> 00:31:36.060 here, a very, very fine dispersion of 00:31:36.060 --> 00:31:37.680 tiny droplets of oil. 00:31:37.680 --> 00:31:41.200 And then-- this cartoon is hard to make sense of so I 00:31:41.200 --> 00:31:42.860 fixed this-- 00:31:42.860 --> 00:31:45.850 we shine high-energy radiation on this. 00:31:45.850 --> 00:31:48.440 And by the action of high energy radiation we take these 00:31:48.440 --> 00:31:51.730 neutral droplets and we turn them into ions. 00:31:51.730 --> 00:31:55.070 We eject electrons. 00:31:55.070 --> 00:31:57.340 And so now these are charged. 00:31:57.340 --> 00:32:00.730 And then we charge the plates. 00:32:00.730 --> 00:32:05.400 So if we have neutral species and they simply come out of 00:32:05.400 --> 00:32:08.020 the atomizer, they'll settle under gravity. 00:32:08.020 --> 00:32:12.090 But now if they're charged and I put a charge on the plates-- 00:32:12.090 --> 00:32:14.310 let's say as here the upper plate is positive-- 00:32:14.310 --> 00:32:17.385 if any of these particles is charged positive, the action 00:32:17.385 --> 00:32:21.140 of the electric field will accelerate the descent, 00:32:21.140 --> 00:32:23.420 because the bottom plate is negative attracting and a 00:32:23.420 --> 00:32:25.490 positive plate at the top is repelling. 00:32:25.490 --> 00:32:26.630 And vice versa. 00:32:26.630 --> 00:32:29.260 If I have a particle that's negative, the upper positive 00:32:29.260 --> 00:32:31.450 plate will actually cause it to slow down, and in the 00:32:31.450 --> 00:32:33.850 extreme, it may actually start to rise. 00:32:33.850 --> 00:32:37.490 And so what Millikan did is a set of experiments in which he 00:32:37.490 --> 00:32:39.880 studied all the different particle sizes. 00:32:39.880 --> 00:32:41.110 See this telescope? 00:32:41.110 --> 00:32:43.170 Right over here is Millikan. 00:32:43.170 --> 00:32:44.790 And Millikan's sitting there and he's 00:32:44.790 --> 00:32:46.240 squirting and he's watching. 00:32:46.240 --> 00:32:48.610 He's measuring the settling velocity. 00:32:48.610 --> 00:32:51.370 And he changes the magnitude of the electric field. 00:32:51.370 --> 00:32:53.590 He changes the intensity of radiation. 00:32:53.590 --> 00:32:55.255 He changes the nozzle. 00:32:55.255 --> 00:32:56.960 He changes everything he can. 00:32:56.960 --> 00:32:58.090 And what does he find? 00:32:58.090 --> 00:33:01.460 He finds that the distribution of velocities is not 00:33:01.460 --> 00:33:03.200 continuous. 00:33:03.200 --> 00:33:04.750 It's not continuous. 00:33:04.750 --> 00:33:07.580 You think, well, gee if you just keep dialing you should 00:33:07.580 --> 00:33:10.020 get every variation of velocity. 00:33:10.020 --> 00:33:11.060 Well, he doesn't. 00:33:11.060 --> 00:33:17.690 He finds that he gets variation down to a single 00:33:17.690 --> 00:33:20.700 value, below which he can't go. 00:33:20.700 --> 00:33:32.440 He determines that electric charge is quantized. 00:33:32.440 --> 00:33:35.080 That is to say there's a base unit. 00:33:35.080 --> 00:33:36.310 It's an element. 00:33:36.310 --> 00:33:39.910 I just talked to you about the elemental building block. 00:33:39.910 --> 00:33:42.470 That's an element in mass space. 00:33:42.470 --> 00:33:43.170 Now I'm going to go 00:33:43.170 --> 00:33:45.790 conceptually into charge space. 00:33:45.790 --> 00:33:49.655 There is an elemental building block of electric charge. 00:33:52.280 --> 00:33:53.840 Electric charge is quantized. 00:33:57.950 --> 00:34:06.450 And he found that the elementary charge, which we 00:34:06.450 --> 00:34:08.270 gave the symbol, e. 00:34:08.270 --> 00:34:10.430 e is not the symbol for electron. 00:34:10.430 --> 00:34:12.580 e is the symbol for elementary charge. 00:34:12.580 --> 00:34:18.030 It has a value, if you convert it to modern SI units, of 1.6 00:34:18.030 --> 00:34:24.385 times 10 to the minus 19 Coulombs. 00:34:24.385 --> 00:34:28.960 So now I can take these two pieces of information, Faraday 00:34:28.960 --> 00:34:31.210 which is up here. 00:34:31.210 --> 00:34:34.190 This is known as the Faraday Constant. 00:34:34.190 --> 00:34:38.810 Script f, Faraday constant. 00:34:38.810 --> 00:34:41.440 So if I divide the Faraday constant, which is the charge 00:34:41.440 --> 00:34:44.470 on a mole of electrons, by the elementary charge, which is 00:34:44.470 --> 00:34:48.010 the charge on one electron, presumably I should end up 00:34:48.010 --> 00:34:49.350 with the Avogadro number. 00:34:49.350 --> 00:34:52.890 It should be the ratio of the Faraday to 00:34:52.890 --> 00:34:54.110 the elementary charge. 00:34:54.110 --> 00:34:55.570 And it gives us-- 00:34:55.570 --> 00:34:56.890 for the third time this morning-- 00:34:56.890 --> 00:35:00.190 6.02 times 10 to the 23rd. 00:35:00.190 --> 00:35:06.590 If you like per mole, yes or no, doesn't matter. 00:35:06.590 --> 00:35:09.050 So now, what's the atomic mass unit? 00:35:09.050 --> 00:35:13.650 Now we can say the atomic mass unit is, 1 atomic mass unit 00:35:13.650 --> 00:35:15.370 then must equal what? 00:35:15.370 --> 00:35:22.590 It's going to equal 1/12 of the mass of carbon 12. 00:35:22.590 --> 00:35:27.420 1/12 of the mass of carbon 12 divided by the Avogadro 00:35:27.420 --> 00:35:34.900 number, which gives us 1.661 times 10 to the minus 27 00:35:34.900 --> 00:35:36.320 kilograms. 00:35:36.320 --> 00:35:39.500 Now be careful because the system is just 00:35:39.500 --> 00:35:40.450 a little bit rickety. 00:35:40.450 --> 00:35:44.590 You know we went SI, but look, this is still defined as 12 00:35:44.590 --> 00:35:49.900 grams. And so sometimes if you look depending on where this 00:35:49.900 --> 00:35:54.510 is, 10 to minus 27 kilograms or 10 to the minus 24 grams. 00:35:54.510 --> 00:35:55.760 Just be careful. 00:35:58.260 --> 00:36:05.040 If you ignore this you'll be off only by factor of 1,000. 00:36:05.040 --> 00:36:05.730 That's a joke. 00:36:05.730 --> 00:36:08.250 But it's lost here. 00:36:08.250 --> 00:36:09.410 People are too serious. 00:36:09.410 --> 00:36:10.660 We'll lighten you up. 00:36:10.660 --> 00:36:13.420 All right, so enough of the history. 00:36:13.420 --> 00:36:15.100 Let's now do something dynamic. 00:36:15.100 --> 00:36:16.930 So far we've been studying static elements. 00:36:16.930 --> 00:36:21.010 But chemistry is really the action of elements in motion. 00:36:21.010 --> 00:36:24.060 So how do we describe a chemical reaction? 00:36:24.060 --> 00:36:25.080 Let's look at that. 00:36:25.080 --> 00:36:29.090 What are the rules to describe a chemical reaction? 00:36:29.090 --> 00:36:31.190 Write an equation. 00:36:31.190 --> 00:36:36.179 Write the equation of the chemical reaction subject to 00:36:36.179 --> 00:36:38.167 these rules. 00:36:38.167 --> 00:36:40.652 There are two simple rules. 00:36:40.652 --> 00:36:45.544 One is conservation of mass. 00:36:45.544 --> 00:36:45.712 We've been told the repeatedly since Democritus, 00:36:45.712 --> 00:36:47.740 conservation of mass. 00:36:47.740 --> 00:36:51.440 And the second thing, we use Dalton's Law of Molar 00:36:51.440 --> 00:36:52.690 Proportions. 00:36:58.120 --> 00:37:02.750 That is to say, the building blocks in integer ratios. 00:37:06.380 --> 00:37:08.950 And so I thought I'd do this in context. 00:37:08.950 --> 00:37:11.710 So I've got a specific example here. 00:37:11.710 --> 00:37:13.940 So this is something that I'm interested in. 00:37:13.940 --> 00:37:17.810 Some of my research is in metallurgical extraction by 00:37:17.810 --> 00:37:18.910 benign processes. 00:37:18.910 --> 00:37:21.400 What you're looking at is a billet of titanium. 00:37:21.400 --> 00:37:23.470 To give you a sense, you can see the stairwell back here. 00:37:23.470 --> 00:37:26.770 So this is about 4 feet, a little over a meter here. 00:37:26.770 --> 00:37:29.720 So you can see this is one honking big piece of titanium. 00:37:29.720 --> 00:37:32.890 This came out of the primary reactor, the Kroll reactor and 00:37:32.890 --> 00:37:36.910 this is subsequently swaged and hot worked and so on to 00:37:36.910 --> 00:37:37.760 form these billets. 00:37:37.760 --> 00:37:41.920 So this is the first step of turning dirt into metal. 00:37:41.920 --> 00:37:43.285 That's called titanium sponge. 00:37:43.285 --> 00:37:48.550 And titanium sponge occurs inside a Kroll reactor. 00:37:48.550 --> 00:37:51.780 It occurs inside a Kroll reactor, which was invented by 00:37:51.780 --> 00:37:56.440 a man of the surname Kroll in Luxembourg in the 1930s. 00:37:56.440 --> 00:37:59.870 And then with the advent of World War II, he decided to be 00:37:59.870 --> 00:38:01.120 smart, to get out. 00:38:01.120 --> 00:38:04.190 And he ended up in Oregon where he became a professor. 00:38:04.190 --> 00:38:06.580 So he's known as Professor Kroll, although the truth be 00:38:06.580 --> 00:38:08.560 told he really made his discovery 00:38:08.560 --> 00:38:09.820 before he became a professor. 00:38:09.820 --> 00:38:12.380 But he's still a professor and so we'll honor him. 00:38:12.380 --> 00:38:19.970 And so the Kroll process for making titanium centers around 00:38:19.970 --> 00:38:21.200 this reaction. 00:38:21.200 --> 00:38:27.280 Here's the reaction written according to the rules above. 00:38:27.280 --> 00:38:30.460 We take titanium dioxide, which is found in the Earth 00:38:30.460 --> 00:38:33.910 and by some prior chemistry convert it to titanium 00:38:33.910 --> 00:38:37.200 tetrachloride, and in a reactor that I'm going to show 00:38:37.200 --> 00:38:39.190 you in a moment, we react titanium 00:38:39.190 --> 00:38:41.150 tetrachloride with magnesium. 00:38:41.150 --> 00:38:44.040 And magnesium has a higher affinity for chlorine than 00:38:44.040 --> 00:38:48.660 does titanium and steals the chlorine from titanium to form 00:38:48.660 --> 00:38:53.130 magnesium chloride, leaving behind titanium metal. 00:38:53.130 --> 00:38:55.760 Now we have to have conservation of mass. 00:38:55.760 --> 00:38:58.860 So you can see, I've got 4 chlorines on the left but only 00:38:58.860 --> 00:39:00.130 2 chlorines on the right. 00:39:00.130 --> 00:39:02.930 So I'm going to put a 2 here and double 00:39:02.930 --> 00:39:04.140 the magnesium chloride. 00:39:04.140 --> 00:39:06.070 But now I've got 2 magnesiums on the right and 00:39:06.070 --> 00:39:07.330 only 1 on the left. 00:39:07.330 --> 00:39:09.920 So I'll put a 2 in front of the magnesium and now we have 00:39:09.920 --> 00:39:11.170 a balanced equation. 00:39:14.100 --> 00:39:17.580 And here's what the reactor looks like. 00:39:17.580 --> 00:39:21.370 You can imagine a giant vessel with a pressure seal on the 00:39:21.370 --> 00:39:24.660 top and a couple of valves, big enough to make this. 00:39:24.660 --> 00:39:27.900 So this is about 15 feet by 30 feet. 00:39:27.900 --> 00:39:32.210 And so we introduce titanium tetrachloride, which is a gas, 00:39:32.210 --> 00:39:36.760 and magnesium as a solid and heat to 900 degrees C. 00:39:36.760 --> 00:39:39.310 And at 900 degrees C, if you look on your Periodic Table 00:39:39.310 --> 00:39:42.450 you'll know that magnesium melts at 650 degrees C. 00:39:42.450 --> 00:39:45.250 So we have a liquid sitting here, titanium tetrachloride 00:39:45.250 --> 00:39:47.830 here, and this thing is sealed. 00:39:47.830 --> 00:39:49.550 It's called a bomb reactor. 00:39:49.550 --> 00:39:51.190 Nothing can get in, nothing can get out. 00:39:51.190 --> 00:39:52.630 The pressure builds up here. 00:39:52.630 --> 00:39:55.100 And right at this interface the titanium tetrachloride 00:39:55.100 --> 00:39:57.840 reacts with the magnesium according to this reaction. 00:39:57.840 --> 00:39:59.280 Now this is very interesting. 00:39:59.280 --> 00:40:01.530 It's beautiful reaction because the titanium 00:40:01.530 --> 00:40:04.880 tetrachloride is a gas; magnesium is a liquid. 00:40:04.880 --> 00:40:07.740 Magnesium chloride is a liquid, but it is of different 00:40:07.740 --> 00:40:11.300 density, and it is insoluble in magnesium, and titanium 00:40:11.300 --> 00:40:13.620 melts at 1670 and it's a solid. 00:40:13.620 --> 00:40:16.260 So what happens over time is this. 00:40:16.260 --> 00:40:19.920 The magnesium chloride that forms pools underneath the 00:40:19.920 --> 00:40:22.790 magnesium liquid, gets out of the way so that we can 00:40:22.790 --> 00:40:25.750 continue to keep this interface clean and have the 00:40:25.750 --> 00:40:26.970 reaction proceed. 00:40:26.970 --> 00:40:31.630 You don't want to reaction where reactant A reacts with 00:40:31.630 --> 00:40:34.710 reactant B, makes a product that covers the interface and 00:40:34.710 --> 00:40:38.000 now the product is in the way of future reaction. 00:40:38.000 --> 00:40:40.760 So this is very elegant because I don't need any fans, 00:40:40.760 --> 00:40:43.420 I don't need any nose propellers, nothing. 00:40:43.420 --> 00:40:46.110 By density the magnesium chloride settles and the 00:40:46.110 --> 00:40:47.370 titanium settles. 00:40:47.370 --> 00:40:48.740 And it's sitting here at the bottom. 00:40:48.740 --> 00:40:51.010 And you can imagine if we do this long enough, this 00:40:51.010 --> 00:40:54.120 titanium at the bottom will continue to build until it 00:40:54.120 --> 00:40:56.190 looks like this. 00:40:56.190 --> 00:40:59.342 As long as you keep feeding TiCl and Mg. 00:40:59.342 --> 00:41:01.160 See I'm talking metallurgy now. 00:41:01.160 --> 00:41:04.980 TiCl and Mg, that's what you make. 00:41:04.980 --> 00:41:08.350 So that's how we make titanium, first step. 00:41:08.350 --> 00:41:12.120 And so suppose you get hired and it's your first day on the 00:41:12.120 --> 00:41:19.500 job and you're working at Cambridge Titanium and the 00:41:19.500 --> 00:41:29.160 boss says let's put in 200 kilograms of TiCl and we'll 00:41:29.160 --> 00:41:34.060 put in 25 kilograms of Mg. 00:41:34.060 --> 00:41:38.590 And the question is, what is the yield? 00:41:38.590 --> 00:41:39.670 What is the yield? 00:41:39.670 --> 00:41:42.590 How much titanium are we going to make? 00:41:42.590 --> 00:41:44.240 Well, you say, just multiply it out. 00:41:44.240 --> 00:41:47.940 But first you have to see if things are in balance. 00:41:47.940 --> 00:41:52.410 We have to study the stoichiometry of the reaction. 00:41:52.410 --> 00:41:54.260 Stoichiometry, what does this mean? 00:41:54.260 --> 00:41:56.590 It's from the Greek, stoicheia, which has to do 00:41:56.590 --> 00:41:59.300 with measurement proportions. 00:41:59.300 --> 00:42:04.740 So if these are not put in to the reactor in proportion to 00:42:04.740 --> 00:42:07.360 what they are in the equation we're not going to get the 00:42:07.360 --> 00:42:08.870 yield here. 00:42:08.870 --> 00:42:12.250 So first thing I gotta do, this is in moles, this is in 00:42:12.250 --> 00:42:15.700 kilograms. So I have to convert the kilograms to moles 00:42:15.700 --> 00:42:17.660 and then maybe I can make some sense of this. 00:42:17.660 --> 00:42:21.255 So if I divide by the atomic mass of titanium, four times 00:42:21.255 --> 00:42:24.910 the atomic mass of chlorine and convert; I will discover 00:42:24.910 --> 00:42:30.770 that I have 1,054 moles of TiCl. 00:42:30.770 --> 00:42:36.770 And I've got about 1,029 moles of magnesium. 00:42:36.770 --> 00:42:43.170 Well, this equation says I need 2 times the amount of 00:42:43.170 --> 00:42:44.160 titanium tetrachloride. 00:42:44.160 --> 00:42:47.180 Well, it's obvious to the naked eye, 1,029 isn't two 00:42:47.180 --> 00:42:49.150 times 1,054. 00:42:49.150 --> 00:42:50.690 So I've got a problem here. 00:42:50.690 --> 00:42:54.290 I'm not going to get as much titanium as I put in. 00:42:54.290 --> 00:42:55.540 Titanium chloride. 00:42:55.540 --> 00:42:57.930 This yield is going to be restricted. 00:42:57.930 --> 00:43:00.510 It's going to be restricted by-- this is sort of a chain 00:43:00.510 --> 00:43:02.420 is as strong as its weakest link-- 00:43:02.420 --> 00:43:06.910 the yield is restricted by the amount of limiting reagent. 00:43:06.910 --> 00:43:11.820 And in this case, magnesium is-- this is less than 2 times 00:43:11.820 --> 00:43:15.630 the mole number of titanium chloride. 00:43:15.630 --> 00:43:17.950 So this means this is the limiting reagent. 00:43:22.510 --> 00:43:26.470 Alright so now if we use that principle then I'm only going 00:43:26.470 --> 00:43:28.910 to get as much titanium as I had magnesium and you can see 00:43:28.910 --> 00:43:32.140 from the stoichiometry here, if I've got 1,029 moles of 00:43:32.140 --> 00:43:33.800 magnesium I'm going to have half of 00:43:33.800 --> 00:43:35.510 that number of titanium. 00:43:35.510 --> 00:43:42.430 So therefore the amount of titanium is equal to 515 moles 00:43:42.430 --> 00:43:43.410 of titanium. 00:43:43.410 --> 00:43:46.730 And you notice I'm not obsessed about a significant 00:43:46.730 --> 00:43:47.600 figures and so on. 00:43:47.600 --> 00:43:49.980 It's a metallurgical plant. 00:43:49.980 --> 00:43:51.990 Half of 1,029 is 515. 00:43:51.990 --> 00:43:53.900 Is it 514.5? 00:43:53.900 --> 00:43:54.590 If you wish. 00:43:54.590 --> 00:43:55.060 I don't care. 00:43:55.060 --> 00:43:59.330 So 515 moles and then I convert that, which gives me 00:43:59.330 --> 00:44:05.430 24.7 kilograms of titanium when I use 00:44:05.430 --> 00:44:07.240 that amount of magnesium. 00:44:07.240 --> 00:44:11.720 And if you go to the text, Section 2.7, you'll see the 00:44:11.720 --> 00:44:14.580 nuts and bolts of how to run these reactions. 00:44:14.580 --> 00:44:16.355 For those of you who had a lot of chemistry in high school, I 00:44:16.355 --> 00:44:18.900 know this is review, but I want to bring everybody up to 00:44:18.900 --> 00:44:20.600 the same page. 00:44:20.600 --> 00:44:23.530 So we're starting with this. 00:44:23.530 --> 00:44:24.070 All right. 00:44:24.070 --> 00:44:26.940 I think that's a pretty good place to 00:44:26.940 --> 00:44:28.930 stop with the delivery. 00:44:28.930 --> 00:44:31.130 But I don't want you moving. 00:44:31.130 --> 00:44:31.690 You don't move yet. 00:44:31.690 --> 00:44:33.080 Because the last 5 minutes I'm going to 00:44:33.080 --> 00:44:34.150 still continue to talk. 00:44:34.150 --> 00:44:36.040 But on a slightly different topic. 00:44:36.040 --> 00:44:38.320 And so I don't want to hear the binders 00:44:38.320 --> 00:44:41.020 snapping and so on. 00:44:41.020 --> 00:44:42.590 We're here; you paid your money. 00:44:42.590 --> 00:44:44.150 Five more minutes. 00:44:44.150 --> 00:44:46.090 Five more minutes and then you're out there. 00:44:46.090 --> 00:44:48.200 Out there, then begins le weekend. 00:44:48.200 --> 00:44:49.820 But not until then. 00:44:49.820 --> 00:44:51.260 So a couple of things. 00:44:51.260 --> 00:44:52.960 First is, the music today. 00:44:52.960 --> 00:44:54.760 I try to link the music thematically. 00:44:54.760 --> 00:45:01.260 So the music playing today was Polovstian Dance number 17 00:45:01.260 --> 00:45:05.510 from Prince Igor, by Borodin, Aleksandr Borodin. 00:45:05.510 --> 00:45:07.210 Why were we listening to this music? 00:45:07.210 --> 00:45:09.870 Well, because I insisted that we listen to it. 00:45:09.870 --> 00:45:11.060 Well, what about Borodin? 00:45:11.060 --> 00:45:13.270 Borodin lived in Saint Petersburg. 00:45:13.270 --> 00:45:14.860 He was a friend of Mendeleyev. 00:45:14.860 --> 00:45:19.100 OK, that's cute but more importantly Borodin wrote his 00:45:19.100 --> 00:45:20.930 music in his leisure time. 00:45:20.930 --> 00:45:22.050 He had a day job. 00:45:22.050 --> 00:45:25.690 His day job was professor of chemistry. 00:45:25.690 --> 00:45:28.570 And he worked at the Medical Surgical Academy in Saint 00:45:28.570 --> 00:45:29.630 Petersburg. 00:45:29.630 --> 00:45:31.920 He was an exceptional human being. 00:45:31.920 --> 00:45:34.980 In those days, women were forbidden to attend 00:45:34.980 --> 00:45:36.830 institutions of higher education. 00:45:36.830 --> 00:45:42.190 He set up an entire curriculum for women in a night school at 00:45:42.190 --> 00:45:44.710 the Medical Surgical Academy. 00:45:44.710 --> 00:45:47.560 He cavorted with artists and therefore obviously his 00:45:47.560 --> 00:45:48.810 politics were radical. 00:45:48.810 --> 00:45:51.890 And they were trying to reform the political scene in Czarist 00:45:51.890 --> 00:45:53.440 Russia at the time. 00:45:53.440 --> 00:45:56.700 And he was also quite a bon vivant. 00:45:56.700 --> 00:46:03.080 And he died on his feet dancing at a ball. 00:46:03.080 --> 00:46:04.570 So that's the way to go. 00:46:04.570 --> 00:46:06.200 Having a great time. 00:46:06.200 --> 00:46:07.450 That was Borodin. 00:46:09.590 --> 00:46:11.160 One other thing before you go. 00:46:11.160 --> 00:46:14.680 You were very very dour, so I thought I'd try to put you in 00:46:14.680 --> 00:46:17.800 a good mood to the extent this is possible with this group. 00:46:17.800 --> 00:46:22.050 And I wanted to share with you some news. 00:46:22.050 --> 00:46:23.780 There's been a new element discovered. 00:46:23.780 --> 00:46:26.640 You know these atoms smashers, they're always working. 00:46:26.640 --> 00:46:29.340 And so the discovery of the heaviest element known to 00:46:29.340 --> 00:46:31.170 science has been reported. 00:46:31.170 --> 00:46:33.750 The element, tentatively named administratium. 00:46:36.900 --> 00:46:39.530 I don't know if UPEC is going to go for this, but you can 00:46:39.530 --> 00:46:41.910 suggest names. 00:46:41.910 --> 00:46:44.430 So they're going to name is administratium, the 00:46:44.430 --> 00:46:47.240 discoverers. 00:46:47.240 --> 00:46:50.830 It has no protons or electrons. 00:46:50.830 --> 00:46:55.500 So that means its atomic number is 0. 00:46:55.500 --> 00:47:00.850 It does have one neutron, 125 assistants to the neutron. 00:47:00.850 --> 00:47:04.820 75 vice-neutrons and a 111 assistants to the 00:47:04.820 --> 00:47:06.360 vice-neutrons. 00:47:06.360 --> 00:47:11.580 This gives it a mass number of 312. 00:47:11.580 --> 00:47:14.660 The 312 particles are held together in the nucleus by a 00:47:14.660 --> 00:47:17.210 force that involves the continuous exchange of 00:47:17.210 --> 00:47:21.430 meson-like particles called memo-ons. 00:47:21.430 --> 00:47:24.470 There's no electronic mail, because there's no electrons. 00:47:24.470 --> 00:47:27.220 There may be neutronic mail but we don't know yet. 00:47:27.220 --> 00:47:29.110 Now you've already learned something today. 00:47:29.110 --> 00:47:30.220 You know something. 00:47:30.220 --> 00:47:32.640 Since it has no electrons, what do we know about its 00:47:32.640 --> 00:47:34.820 chemical reactivity? 00:47:34.820 --> 00:47:35.805 It's inert. 00:47:35.805 --> 00:47:37.080 It has no electrons. 00:47:37.080 --> 00:47:38.230 It can't exchange. 00:47:38.230 --> 00:47:39.450 So this is chemically inert. 00:47:39.450 --> 00:47:42.920 So you say, how did they detect it? 00:47:42.920 --> 00:47:44.940 Because it seems to impede every reaction in 00:47:44.940 --> 00:47:46.190 which it is a present. 00:47:49.290 --> 00:47:53.010 According to the discoverers a few nanograms rendered a 00:47:53.010 --> 00:47:58.420 reaction that normally takes a fraction of a second, it took 00:47:58.420 --> 00:48:01.635 now four business days to conduct that same. 00:48:04.450 --> 00:48:07.370 There are a few other properties. 00:48:07.370 --> 00:48:10.030 We know so far that it's radioactive. 00:48:10.030 --> 00:48:11.990 And we're going to study radioactivity later, so 00:48:11.990 --> 00:48:13.830 there's a little bit of foreshadowing. 00:48:13.830 --> 00:48:16.850 It has a half-life of about three years, at which time it 00:48:16.850 --> 00:48:22.240 stops decaying and instead it undergoes a reorganization, in 00:48:22.240 --> 00:48:24.780 which the vice-neutrons, assistants to the neutrons and 00:48:24.780 --> 00:48:25.310 assistants to the 00:48:25.310 --> 00:48:27.810 vice-neutrons, exchange places. 00:48:27.810 --> 00:48:32.040 Some studies indicate that the mass actually increases after 00:48:32.040 --> 00:48:33.760 each reorganization. 00:48:33.760 --> 00:48:36.970 So you can imagine now we'll have something like this. 00:48:40.590 --> 00:48:43.270 See how this increased? 00:48:43.270 --> 00:48:47.370 So if they occupy the same place, they have the same 00:48:47.370 --> 00:48:51.110 proton number, but a different neutron number, in the case of 00:48:51.110 --> 00:48:55.080 administratium, they're called isodopes. 00:48:55.080 --> 00:48:57.820 So with that I will say, have a good weekend.