1 00:00:16,967 --> 00:00:19,603 Now, today is lecture 2. 2 00:00:19,703 --> 00:00:23,640 And we're going to be talking about counting. 3 00:00:23,741 --> 00:00:26,744 And we're going to be talking about the mul which is a way 4 00:00:26,844 --> 00:00:29,413 to count to help us count. 5 00:00:29,513 --> 00:00:32,316 And then-- and this is really exciting-- 6 00:00:32,415 --> 00:00:33,684 we're going to be building this. 7 00:00:33,784 --> 00:00:34,852 And that is super exciting. 8 00:00:34,952 --> 00:00:36,220 Now, everybody should have gotten 9 00:00:36,320 --> 00:00:39,423 one of these on the first day when 10 00:00:39,523 --> 00:00:41,458 we talk about this later in the lecture. 11 00:00:41,558 --> 00:00:44,828 If you don't have this, and for that matter-- 12 00:00:44,928 --> 00:00:45,863 oh, there's Laura. 13 00:00:45,963 --> 00:00:48,332 Laura has like thousands of these. 14 00:00:48,432 --> 00:00:51,568 And if you need one, please ask Laura. 15 00:00:51,668 --> 00:00:53,637 And also if you need a goodie bag, 16 00:00:53,737 --> 00:00:55,506 which we gave out on the first day, 17 00:00:55,606 --> 00:00:56,974 please get in touch with Laura. 18 00:00:57,074 --> 00:00:58,042 And she'll give you one. 19 00:00:58,142 --> 00:00:59,343 We have extras here. 20 00:00:59,443 --> 00:01:03,747 You can stop by our office later, get one please today. 21 00:01:03,847 --> 00:01:08,952 All right, now, last lecture, we left off with-- 22 00:01:09,053 --> 00:01:14,658 remember, those guys like Boyle and Priestley and Lavoisier, 23 00:01:14,758 --> 00:01:16,460 conservation of mass, right? 24 00:01:16,560 --> 00:01:20,230 And what these guys were doing is 25 00:01:20,330 --> 00:01:24,268 they were smashing and burning and pushing on things 26 00:01:24,368 --> 00:01:28,038 and trying to figure out what it was 27 00:01:28,138 --> 00:01:32,776 that was that sort of fundamental object 28 00:01:32,876 --> 00:01:35,412 that you couldn't break apart anymore. 29 00:01:35,512 --> 00:01:38,247 And remember, it was Democritus that said 30 00:01:38,348 --> 00:01:40,283 there is such a thing, right? 31 00:01:40,384 --> 00:01:44,922 He said there was a such a thing called atoms, "atomos". 32 00:01:45,021 --> 00:01:46,557 And so we come to Dalton, who said, 33 00:01:46,657 --> 00:01:48,158 look, these things we're trying, we're 34 00:01:48,258 --> 00:01:50,727 calling them elements right now. 35 00:01:50,828 --> 00:01:54,832 Let's, in honor of that indivisibility idea, 36 00:01:54,932 --> 00:01:57,601 let's call them atoms. 37 00:01:57,701 --> 00:02:01,472 And Dalton did a lot of really important experiments. 38 00:02:01,572 --> 00:02:05,275 And he was also trying to smash and break and measure 39 00:02:05,375 --> 00:02:08,544 and figure out what are these indivisible-- 40 00:02:08,645 --> 00:02:12,816 and what are these things that you can't break apart any more? 41 00:02:12,916 --> 00:02:14,051 What are these atoms? 42 00:02:14,151 --> 00:02:16,153 How many of them are there? 43 00:02:16,253 --> 00:02:17,888 What do they do? 44 00:02:17,988 --> 00:02:22,593 And he came up with a pretty important observation 45 00:02:22,693 --> 00:02:28,198 which was that he called it the law of multiple proportions. 46 00:02:28,298 --> 00:02:35,038 And in this, so what Dalton did is he said, 47 00:02:35,139 --> 00:02:39,109 look, I'm going to take something and react it 48 00:02:39,209 --> 00:02:40,811 with something else. 49 00:02:40,911 --> 00:02:43,280 And it's going to react fully. 50 00:02:43,380 --> 00:02:45,616 OK, so there's no limiting reagent. 51 00:02:45,716 --> 00:02:46,884 There's no excess. 52 00:02:46,984 --> 00:02:49,286 It just everything reacted here and everything 53 00:02:49,386 --> 00:02:52,189 and want to measure how much stuff reacts. 54 00:02:52,289 --> 00:02:54,291 And then how much I get. 55 00:02:54,391 --> 00:02:57,194 And so if you take like an example 56 00:02:57,293 --> 00:03:02,065 of this law of multiple proportions, 57 00:03:02,166 --> 00:03:04,601 if you take an example of how that came about, 58 00:03:04,701 --> 00:03:08,605 what he observed is that if you had sort of, for example, 59 00:03:08,705 --> 00:03:12,409 maybe you had sort of case one. 60 00:03:12,509 --> 00:03:14,978 And you react some amount. 61 00:03:15,078 --> 00:03:17,079 So he's going to react some amount. 62 00:03:17,181 --> 00:03:19,583 So let's say he reacted-- 63 00:03:19,683 --> 00:03:21,985 OK, I don't know, some amount. 64 00:03:22,085 --> 00:03:23,353 Let's write it. 65 00:03:23,453 --> 00:03:28,492 Yeah, some amount of something, maybe, carbon. 66 00:03:28,591 --> 00:03:33,597 And some amount of something else. 67 00:03:33,697 --> 00:03:35,432 How about oxygen? 68 00:03:35,531 --> 00:03:38,569 And he would get some amount, right? 69 00:03:38,668 --> 00:03:41,672 OK, we know he's doing all these measurements. 70 00:03:41,772 --> 00:03:43,540 I'm trying to get you back in that mood. 71 00:03:43,640 --> 00:03:44,474 How much do I have? 72 00:03:44,575 --> 00:03:45,942 I'm going to weigh it, measure it. 73 00:03:46,043 --> 00:03:47,477 That's what he's doing over and over. 74 00:03:47,578 --> 00:03:51,281 But he had some amount of something. 75 00:03:51,381 --> 00:03:53,350 Aha. 76 00:03:53,450 --> 00:03:56,653 Now, he would do this over and over again. 77 00:03:56,753 --> 00:03:59,623 OK, I'm just taking these two elements as an example. 78 00:03:59,723 --> 00:04:02,492 He did this for many, many elements, right? 79 00:04:02,593 --> 00:04:04,428 So some amount of carbon with salmonella. 80 00:04:04,528 --> 00:04:08,432 And in case one, OK, everything reacts. 81 00:04:08,532 --> 00:04:16,072 And I get this carbon to oxygen mass ratio of let's say 82 00:04:16,173 --> 00:04:19,875 1 to 1.33. 83 00:04:19,976 --> 00:04:20,543 I measure it. 84 00:04:23,380 --> 00:04:26,350 That's how much of the sum amount, right? 85 00:04:26,450 --> 00:04:31,555 1 to 1.33 reacts fully. 86 00:04:31,655 --> 00:04:34,591 Remember, no excess, because they add a little more, 87 00:04:34,691 --> 00:04:35,359 and it's excess. 88 00:04:35,459 --> 00:04:38,462 No, this reacts fully. 89 00:04:38,562 --> 00:04:41,331 And then you do it, again, case 2. 90 00:04:41,431 --> 00:04:47,771 And he'd find that this same ratio was 1 to 2.66. 91 00:04:47,871 --> 00:04:49,139 Ha, ha. 92 00:04:49,239 --> 00:04:51,642 And he noticed a pattern. 93 00:04:51,742 --> 00:04:53,210 And he noticed a pattern. 94 00:04:53,310 --> 00:04:55,012 And he called it the law multiple portions, 95 00:04:55,112 --> 00:04:58,815 because what he found is that you could keep on going. 96 00:04:58,915 --> 00:05:01,918 And in some cases, not all cases. 97 00:05:02,019 --> 00:05:04,121 But in some cases, like carbon and oxygen, 98 00:05:04,221 --> 00:05:10,627 for example, these were common ratios, these series. 99 00:05:10,727 --> 00:05:15,465 2.66 divided by 1.33 is an integer. 100 00:05:15,565 --> 00:05:20,804 These things would happen in integer ratios, integer amount. 101 00:05:20,904 --> 00:05:24,574 So I could keep going, and maybe I'd get three or four. 102 00:05:24,675 --> 00:05:25,542 Right? 103 00:05:25,642 --> 00:05:27,311 And what that means is that well, 104 00:05:27,411 --> 00:05:30,180 over here, this sum amount of something 105 00:05:30,280 --> 00:05:33,817 is it said something about the something, 106 00:05:33,917 --> 00:05:40,557 right, because it says maybe these somethings are like CO 107 00:05:40,657 --> 00:05:45,495 and CO2, right, for example. 108 00:05:45,595 --> 00:05:49,533 Maybe, aha, but not definitely. 109 00:05:49,633 --> 00:05:51,068 And that frustrated Dalton. 110 00:05:51,168 --> 00:05:52,602 That frustrated him. 111 00:05:52,703 --> 00:05:54,571 We'll come back to that in a sec. 112 00:05:54,671 --> 00:05:56,306 Right? 113 00:05:56,406 --> 00:05:57,541 But he did this. 114 00:05:57,641 --> 00:06:02,679 And he observed these ratios, these integer ratios 115 00:06:02,779 --> 00:06:05,782 of what would react with what-- he's trying to figure out 116 00:06:05,882 --> 00:06:08,085 what is he making? 117 00:06:08,185 --> 00:06:09,386 All right, what is he making? 118 00:06:12,556 --> 00:06:16,293 Now, he also, as with Lavoisier, remember, 119 00:06:16,393 --> 00:06:19,096 I showed you Lavoisier's tableau. 120 00:06:19,196 --> 00:06:22,165 Well, he had his own table. 121 00:06:22,265 --> 00:06:23,467 And here it is. 122 00:06:23,567 --> 00:06:29,840 So here in 1827, he had identified 36 elements. 123 00:06:29,940 --> 00:06:32,743 Now, the thing is, though, OK, 0.1, 124 00:06:32,843 --> 00:06:35,645 if you're going to try to brand something, which he clearly 125 00:06:35,746 --> 00:06:37,514 tried with these symbols, you can't make 126 00:06:37,614 --> 00:06:40,317 them this complicated, right? 127 00:06:40,417 --> 00:06:43,920 I'm pretty happy that that's not how we write our elements. 128 00:06:44,020 --> 00:06:45,622 You can see that this would be very hard. 129 00:06:45,722 --> 00:06:47,824 But he did come up with these symbols. 130 00:06:47,924 --> 00:06:50,093 And you can see it would be very hard to keep going 131 00:06:50,193 --> 00:06:51,428 without getting [inaudible]. 132 00:06:51,528 --> 00:06:53,697 So I think we're pretty lucky that [? brazilious ?] came 133 00:06:53,797 --> 00:06:56,400 along and figured out how to name these elements 134 00:06:56,500 --> 00:06:59,336 in a consistent way. 135 00:06:59,436 --> 00:07:00,737 But that wasn't his real problem. 136 00:07:00,837 --> 00:07:04,174 His real problem was what I just alluded to. 137 00:07:04,274 --> 00:07:08,879 See, he knew that he had these different elements. 138 00:07:08,979 --> 00:07:11,648 But he didn't know what the compositions were. 139 00:07:11,748 --> 00:07:13,984 He was so close. 140 00:07:14,084 --> 00:07:15,318 He was so close. 141 00:07:15,419 --> 00:07:16,653 He could see that these-- 142 00:07:16,753 --> 00:07:19,289 ah, but is it CO and CO2? 143 00:07:19,389 --> 00:07:21,957 Or is it CO2 and CO4? 144 00:07:22,058 --> 00:07:23,727 That he didn't know. 145 00:07:23,827 --> 00:07:27,531 That he didn't know, because he didn't have an accurate way 146 00:07:27,631 --> 00:07:31,635 to measure the mass of an atom, not at that time. 147 00:07:31,735 --> 00:07:36,473 But he did have this nice ability to see these series. 148 00:07:36,573 --> 00:07:37,307 OK. 149 00:07:37,407 --> 00:07:40,409 But in comes other measurements. 150 00:07:40,510 --> 00:07:47,117 And you had Gay-Lussac who was looking at volumes, right? 151 00:07:47,217 --> 00:07:48,752 And so Gay-Lussac was saying, well, 152 00:07:48,852 --> 00:07:54,791 look, if I take a certain amount of volume of a gas, one gas, 153 00:07:54,891 --> 00:07:59,062 and I reacted again completely, no access, OK? 154 00:07:59,162 --> 00:08:01,898 And I reacted with another gas. 155 00:08:01,998 --> 00:08:05,035 And then I see I get something else over here. 156 00:08:05,135 --> 00:08:06,436 I can measure the volumes. 157 00:08:06,536 --> 00:08:08,805 And I do this for the cases where 158 00:08:08,905 --> 00:08:12,909 there's nothing left over, nothing limited it. 159 00:08:13,009 --> 00:08:17,614 And so he would find, for example, what's shown up there. 160 00:08:17,714 --> 00:08:22,018 He would find that you've got for every two 161 00:08:22,118 --> 00:08:24,888 volumes of hydrogen gas-- 162 00:08:24,988 --> 00:08:27,057 so you've got two volumes of hydrogen 163 00:08:27,157 --> 00:08:34,764 that he would react with one volume of oxygen. 164 00:08:34,865 --> 00:08:37,701 And he would notice that he would get two 165 00:08:37,801 --> 00:08:40,971 volumes of something that had-- 166 00:08:41,071 --> 00:08:42,205 let's not put a dash there-- 167 00:08:42,304 --> 00:08:45,275 it had hydrogen and oxygen in it. 168 00:08:45,375 --> 00:08:46,443 He knew that. 169 00:08:46,543 --> 00:08:49,579 Now, he knew this because he was very careful. 170 00:08:49,679 --> 00:08:50,881 So nothing leaked. 171 00:08:50,981 --> 00:08:51,648 He said no. 172 00:08:51,748 --> 00:08:53,216 Everything is accounted for. 173 00:08:53,316 --> 00:08:56,786 Lavoisier holds-- conservation of mass. 174 00:08:56,887 --> 00:08:58,555 I'm not losing anything here. 175 00:08:58,655 --> 00:09:01,491 And as Lavoisier said, in a chemical reaction, 176 00:09:01,591 --> 00:09:05,295 mass is neither created nor destroyed. 177 00:09:05,395 --> 00:09:09,132 So I know that whatever is over here 178 00:09:09,232 --> 00:09:11,768 must consist of whatever I have here-- 179 00:09:11,868 --> 00:09:16,439 oxygen and hydrogen. And he kept doing it 180 00:09:16,540 --> 00:09:20,644 for other lots of different types of gases. 181 00:09:20,744 --> 00:09:27,250 But it was very strange, because what happens is sometimes, 182 00:09:27,350 --> 00:09:29,119 the volumes are the same. 183 00:09:29,219 --> 00:09:31,221 Like he did it for hydrogen and chlorine. 184 00:09:31,321 --> 00:09:36,960 One volume of hydrogen, and one volume of chlorine 185 00:09:37,060 --> 00:09:41,298 would give you two volumes of hydrogen and chlorine-- 186 00:09:41,398 --> 00:09:44,634 something that had hydrogen and chlorine in it. 187 00:09:44,734 --> 00:09:48,071 And so there, you'd mix one and add another one. 188 00:09:48,171 --> 00:09:49,105 And you'd get two. 189 00:09:49,205 --> 00:09:50,540 It seems it would kind of makes sense. 190 00:09:50,640 --> 00:09:52,342 You add one volume. 191 00:09:52,442 --> 00:09:57,514 But here, you'd mix two volumes, add another volume. 192 00:09:57,614 --> 00:10:00,984 And it would feel like it was reduced. 193 00:10:01,084 --> 00:10:03,753 Something in the reaction happened 194 00:10:03,853 --> 00:10:06,389 that gave you a lower volume. 195 00:10:06,489 --> 00:10:08,191 What could it possibly be? 196 00:10:08,291 --> 00:10:09,826 Right, what was going on. 197 00:10:09,926 --> 00:10:11,528 This is what they were grappling with. 198 00:10:11,628 --> 00:10:13,597 This is where they were. 199 00:10:13,697 --> 00:10:19,536 And then along comes [sighs] Avogadro. 200 00:10:19,636 --> 00:10:25,075 Now, I wish we all called him Lorenzo Romano Amedeo Carlo 201 00:10:25,175 --> 00:10:27,911 Avogadro which is his full name. 202 00:10:28,011 --> 00:10:31,448 But we shall call him Avogadro. 203 00:10:31,548 --> 00:10:36,620 And he made a critical proposal. 204 00:10:36,720 --> 00:10:41,057 He said, look, the way to explain what's 205 00:10:41,157 --> 00:10:45,528 going on in Gay-Lussac's volume measurements 206 00:10:45,629 --> 00:10:50,165 is to make the following assumption-- oh, I 207 00:10:50,266 --> 00:10:52,202 have another board over here-- is to make 208 00:10:52,302 --> 00:10:54,371 the following assumption. 209 00:10:54,471 --> 00:10:57,574 And I think if you've had high school chemistry, 210 00:10:57,674 --> 00:10:59,075 you know what this is. 211 00:10:59,175 --> 00:11:02,846 But I'm going to put it here, because of how important it is. 212 00:11:02,946 --> 00:11:09,753 So Avogadro said that at constant temperature 213 00:11:09,853 --> 00:11:23,566 and pressure equal volume equals same number of particles. 214 00:11:28,204 --> 00:11:30,173 So if I have the [? efomethesine ?] temperature 215 00:11:30,273 --> 00:11:32,709 [inaudible],, if I have the same volume, 216 00:11:32,809 --> 00:11:34,444 I have the same number of [? particles. ?] 217 00:11:34,544 --> 00:11:35,712 Now, what are those particles? 218 00:11:35,812 --> 00:11:37,313 Oh, he was flexible. 219 00:11:37,414 --> 00:11:38,114 This is important. 220 00:11:38,214 --> 00:11:39,115 He was flexible. 221 00:11:39,215 --> 00:11:40,283 He said, those particles could be atoms, 222 00:11:40,383 --> 00:11:42,318 or they could be combinations of atoms. 223 00:11:42,419 --> 00:11:44,287 They could be molecules. 224 00:11:44,387 --> 00:11:46,456 Remember, at the time, they hadn't all 225 00:11:46,556 --> 00:11:49,759 settled on the atom as a name, even. 226 00:11:49,859 --> 00:11:52,095 What were these things? 227 00:11:52,195 --> 00:11:54,230 Equal volume, same number of particles. 228 00:11:54,330 --> 00:11:57,267 And this really helped, because you see, 229 00:11:57,367 --> 00:12:03,373 if you make that assumption, and you believe these volume 230 00:12:03,473 --> 00:12:07,911 measurements, then it becomes very clear what you have there. 231 00:12:08,011 --> 00:12:10,447 Right? 232 00:12:10,547 --> 00:12:13,450 If I have the same number of particles in here, 233 00:12:13,550 --> 00:12:16,019 and I believe in Lavoisier, who tells me nothing 234 00:12:16,119 --> 00:12:17,787 comes in or out in terms of the math, 235 00:12:17,887 --> 00:12:19,155 I didn't create or destroy atoms, 236 00:12:19,255 --> 00:12:23,426 then you know that if I have two volumes of water, 237 00:12:23,526 --> 00:12:28,364 let's say I started with o and h. 238 00:12:28,465 --> 00:12:29,532 It doesn't work. 239 00:12:29,632 --> 00:12:33,103 I can't make enough water. 240 00:12:33,203 --> 00:12:35,038 I just can't make enough particles. 241 00:12:35,138 --> 00:12:37,173 The number of particles on the right 242 00:12:37,273 --> 00:12:40,744 has to be equal to the number of particles 243 00:12:40,844 --> 00:12:43,880 in those two volumes of hydrogen. It's got to add up. 244 00:12:43,980 --> 00:12:46,850 Counting has to work. 245 00:12:46,950 --> 00:12:51,354 That's what Avogadro gave us is this idea of counting. 246 00:12:51,454 --> 00:12:53,823 And that's why we've named a constant after him. 247 00:12:53,923 --> 00:12:54,991 So I'll get to-- 248 00:12:55,091 --> 00:13:00,163 Gesundheit or in honor of Avogadro, "salu-tay". 249 00:13:00,263 --> 00:13:02,165 [laughter] 250 00:13:02,265 --> 00:13:02,899 He was Italian. 251 00:13:05,602 --> 00:13:10,140 And so if you believe Avogadro, if you believe Avogadro, 252 00:13:10,240 --> 00:13:15,078 this becomes clear, because the only way for these things 253 00:13:15,178 --> 00:13:19,282 to work then is if here I'm counting 254 00:13:19,382 --> 00:13:20,817 how much volume's here. 255 00:13:20,917 --> 00:13:25,421 So here I got HCL only if this is a two, and that's a two-- 256 00:13:25,522 --> 00:13:26,356 diatomic gases. 257 00:13:29,526 --> 00:13:31,227 That's the only way the numbers work. 258 00:13:31,327 --> 00:13:34,664 And here, I've got to have two and two. 259 00:13:34,764 --> 00:13:36,599 And this must be H2O. 260 00:13:36,699 --> 00:13:41,171 Oh, or at least it's one simple and very plausible 261 00:13:41,271 --> 00:13:46,576 explanation if Avogadro's hypothesis was right. 262 00:13:46,676 --> 00:13:48,845 Dalton didn't buy it. 263 00:13:48,945 --> 00:13:51,614 Dalton said, uh, uh, no way. 264 00:13:51,714 --> 00:13:53,183 You've got leeks, dude. 265 00:13:53,283 --> 00:13:55,852 And he really was harsh. 266 00:13:58,655 --> 00:14:02,592 Everybody thought water was OH at the time. 267 00:14:02,692 --> 00:14:05,061 And so Dalton said, you must have made a mistake. 268 00:14:05,161 --> 00:14:07,096 I block you on Instagram. 269 00:14:07,197 --> 00:14:08,464 [laughter] 270 00:14:08,565 --> 00:14:10,533 I block you. 271 00:14:10,633 --> 00:14:13,803 And it was pretty tough, because Avogadro 272 00:14:13,903 --> 00:14:15,638 put a lot of really brilliant work 273 00:14:15,738 --> 00:14:19,442 out there that was really ignored for 50 years 274 00:14:19,542 --> 00:14:23,146 until Cannizzaro came along and others. 275 00:14:23,246 --> 00:14:25,548 50 years later, two years after he died 276 00:14:25,648 --> 00:14:28,852 was when we had the first evidence 277 00:14:28,952 --> 00:14:31,454 that the scientific community was willing to believe 278 00:14:31,554 --> 00:14:33,423 that his hypothesis was right. 279 00:14:33,523 --> 00:14:35,892 What a big deal his work was. 280 00:14:40,029 --> 00:14:40,730 OK. 281 00:14:40,830 --> 00:14:42,332 Now, I mentioned that this is-- 282 00:14:42,432 --> 00:14:44,234 I'm mentioning all this because we 283 00:14:44,334 --> 00:14:48,738 are going to use his constant a lot, the Avogadro constant. 284 00:14:48,838 --> 00:14:50,707 And it's a way-- 285 00:14:50,807 --> 00:14:52,809 and so I want to talk about that constant-- 286 00:14:52,909 --> 00:14:55,712 and I want to do it in the context of our candle. 287 00:14:55,812 --> 00:14:59,382 And so because this constant, this number, 288 00:14:59,482 --> 00:15:02,585 this idea of the number of particles 289 00:15:02,685 --> 00:15:09,859 you have in chemistry is the link between the atomic world 290 00:15:09,959 --> 00:15:11,427 and the macroscopic world. 291 00:15:11,527 --> 00:15:13,963 That's what his constant does for us. 292 00:15:14,063 --> 00:15:14,898 OK? 293 00:15:14,998 --> 00:15:16,399 Now, let's put that into context. 294 00:15:16,499 --> 00:15:22,138 If I were to ask you a question like this, I have that candle. 295 00:15:22,238 --> 00:15:24,607 Remember, the candle, the C25H52. 296 00:15:27,343 --> 00:15:30,146 And I say, well, OK, you've lit the candle. 297 00:15:30,246 --> 00:15:32,448 How many candle molecules burn in a minute? 298 00:15:32,548 --> 00:15:33,583 I want to know that. 299 00:15:33,683 --> 00:15:35,118 Don't we all? 300 00:15:35,218 --> 00:15:36,085 Right? 301 00:15:36,185 --> 00:15:37,487 That's a pretty important question. 302 00:15:37,587 --> 00:15:38,821 Why are people nodding? 303 00:15:38,922 --> 00:15:41,257 Thank you for that agreement. 304 00:15:41,357 --> 00:15:43,393 And I could say, well, I assume the 12-hour candle 305 00:15:43,493 --> 00:15:44,928 of the mass and 90 grams, let's get 306 00:15:45,028 --> 00:15:47,630 that off of a candle on Amazon. 307 00:15:47,730 --> 00:15:48,631 Right? 308 00:15:48,731 --> 00:15:50,466 How many molecules burn in a minute? 309 00:15:50,566 --> 00:15:52,635 What I need to know is, well, how many 310 00:15:52,735 --> 00:15:53,870 are we sort of talking about? 311 00:15:53,970 --> 00:15:56,773 How do we know how to even answer this question? 312 00:15:56,873 --> 00:15:58,441 And it comes from the link. 313 00:15:58,540 --> 00:16:01,177 But see, to answer this kind of question, 314 00:16:01,277 --> 00:16:03,913 which I'm sure so many people wanted to know back then, 315 00:16:04,013 --> 00:16:08,318 you must have a way to talk about big numbers. 316 00:16:08,418 --> 00:16:09,585 You must. 317 00:16:09,686 --> 00:16:10,987 Why? 318 00:16:11,087 --> 00:16:14,757 Because there's a lot of these molecules in a very tiny amount 319 00:16:14,857 --> 00:16:15,792 of volume-- 320 00:16:15,892 --> 00:16:18,161 a lot. 321 00:16:18,261 --> 00:16:22,832 Drop of water for perspective has 10 trillion molecules-- 322 00:16:22,932 --> 00:16:25,635 10 trillion molecules. 323 00:16:25,735 --> 00:16:29,005 Anybody know how many cells you have in your body? 324 00:16:29,105 --> 00:16:31,741 600 trillion? 325 00:16:31,841 --> 00:16:34,377 Let's call it 100 trillion just to be nice. 326 00:16:34,477 --> 00:16:35,144 Right? 327 00:16:35,244 --> 00:16:38,047 It's a 100 trillion cells. 328 00:16:38,147 --> 00:16:41,584 And so if you're going to talk about how many cells you have, 329 00:16:41,684 --> 00:16:44,354 or how many molecules are in a drop of water, 330 00:16:44,454 --> 00:16:48,257 you need to have a big number, a big scale. 331 00:16:48,358 --> 00:16:50,593 And that is what a mole is. 332 00:16:53,563 --> 00:16:55,531 Avogadro didn't come up with this number. 333 00:16:55,631 --> 00:16:58,101 This was gotten much later, right? 334 00:16:58,201 --> 00:17:00,269 But we name it after him in honor 335 00:17:00,370 --> 00:17:05,208 of the work he did on counting atoms and molecules. 336 00:17:05,308 --> 00:17:06,342 And that's the number. 337 00:17:06,442 --> 00:17:08,544 This is the way we talk about it. 338 00:17:08,644 --> 00:17:12,949 And just to be complete, Avogadro's constant, 339 00:17:13,049 --> 00:17:22,090 which is a mole, one mole is equal to 6.022 times 10 340 00:17:22,191 --> 00:17:23,826 to the 23rd. 341 00:17:23,925 --> 00:17:26,362 It's just a number. 342 00:17:26,462 --> 00:17:27,030 All right? 343 00:17:27,130 --> 00:17:28,865 It's just a number. 344 00:17:28,965 --> 00:17:32,301 But it's a really important one because it provides the link. 345 00:17:36,572 --> 00:17:41,144 OK, if I take like how many eggs are there in a dozen eggs. 346 00:17:41,244 --> 00:17:42,478 It's 12. 347 00:17:42,578 --> 00:17:46,049 How many bags of sugar are there in a dozen bags of sugar? 348 00:17:46,149 --> 00:17:47,550 It's 12. 349 00:17:47,650 --> 00:17:48,818 All right? 350 00:17:48,918 --> 00:17:52,221 How many atoms are there in a mole of atoms? 351 00:17:52,321 --> 00:17:54,657 That number. 352 00:17:54,757 --> 00:17:55,425 That's all it is. 353 00:17:55,558 --> 00:17:56,793 It's a number. 354 00:17:56,893 --> 00:17:57,994 OK? 355 00:17:58,094 --> 00:18:02,398 Oh, but a dozen eggs weighs differently 356 00:18:02,498 --> 00:18:04,634 than a dozen bags of sugar. 357 00:18:04,734 --> 00:18:08,204 So a mole of one atom will have a different amount 358 00:18:08,304 --> 00:18:12,475 of mass, a different weight than a mole of another atom. 359 00:18:12,575 --> 00:18:15,344 And that's the link that he gave us. 360 00:18:15,445 --> 00:18:17,580 That's the link that this number gave us. 361 00:18:17,680 --> 00:18:21,918 And, in particular, again, going back to this idea of counting, 362 00:18:22,018 --> 00:18:26,923 we can count now with this link. 363 00:18:27,023 --> 00:18:29,325 If I said, how many pennies are there? 364 00:18:29,425 --> 00:18:32,361 And I gave you a mass of pennies, right? 365 00:18:32,462 --> 00:18:36,632 If I had 2.5 kilograms of pennies, 366 00:18:36,732 --> 00:18:39,102 and I say how many pennies do I have? 367 00:18:39,202 --> 00:18:42,071 Then all I need to know is how much each penny weighs. 368 00:18:42,171 --> 00:18:43,906 I'm not going to count them. 369 00:18:44,006 --> 00:18:45,408 Right, you don't want to count them. 370 00:18:45,508 --> 00:18:47,810 You want to do something a little easier. 371 00:18:47,910 --> 00:18:54,016 So if I have one penny, weighs 2.5 grams. 372 00:18:54,117 --> 00:18:57,386 Then I know that I can just get this really easily. 373 00:18:57,487 --> 00:19:01,057 I have 1,000 pennies. 374 00:19:01,157 --> 00:19:03,126 OK. 375 00:19:03,226 --> 00:19:04,760 What a mole does-- 376 00:19:04,861 --> 00:19:06,629 a mole gives us the link. 377 00:19:06,729 --> 00:19:11,734 So a mole, if I have moles, then I 378 00:19:11,834 --> 00:19:16,506 can go to the mass of an atom-- 379 00:19:16,606 --> 00:19:19,442 the mass of an atom. 380 00:19:19,542 --> 00:19:23,513 And from that, I can go all the way up to grams. 381 00:19:26,382 --> 00:19:28,384 And this is critical. 382 00:19:28,484 --> 00:19:29,485 OK. 383 00:19:29,585 --> 00:19:34,223 The mass of the atom and the grams per mole 384 00:19:34,323 --> 00:19:35,391 are the same number. 385 00:19:35,491 --> 00:19:38,828 That's what the mole gives us. 386 00:19:38,928 --> 00:19:41,297 Right. 387 00:19:41,397 --> 00:19:47,703 So in the case of carbon, carbon has 388 00:19:47,803 --> 00:19:54,310 a mass per atom of 12.011 AMU. 389 00:19:54,410 --> 00:19:58,848 These are atomic mass units. 390 00:19:58,948 --> 00:20:01,050 It's just a way to measure things 391 00:20:01,150 --> 00:20:03,052 that have very little mass. 392 00:20:03,152 --> 00:20:06,589 But the link here is that if I have a mole of these things, 393 00:20:06,689 --> 00:20:12,628 if I have a mole, one mole of carbon, then 394 00:20:12,728 --> 00:20:19,502 I have exactly 12.011 grams. 395 00:20:19,602 --> 00:20:22,104 Back and forth, grams, atoms. 396 00:20:22,205 --> 00:20:25,908 Numbers of atoms, mass per atom. 397 00:20:26,008 --> 00:20:28,177 All right, so one carbon atom has 398 00:20:28,277 --> 00:20:31,681 a mass of 12 atomic mass units. 399 00:20:31,781 --> 00:20:33,583 We don't need to know. 400 00:20:33,683 --> 00:20:36,919 This comes from weighing neutrons and protons. 401 00:20:37,019 --> 00:20:39,889 All right, we'll get to that next week. 402 00:20:39,989 --> 00:20:41,157 We don't even know that yet. 403 00:20:41,257 --> 00:20:45,728 But this is a mass of things that the very tiny scale. 404 00:20:45,828 --> 00:20:49,765 And if I have a mole of those atoms, I get to grams. 405 00:20:49,865 --> 00:20:50,633 OK? 406 00:20:50,733 --> 00:20:51,701 So it's my link. 407 00:20:51,801 --> 00:20:54,503 Now, where is this amount? 408 00:20:54,604 --> 00:20:58,107 Where is this critical number that 409 00:20:58,207 --> 00:21:00,743 gives me the counting per gram? 410 00:21:00,843 --> 00:21:05,715 It's, of course, here in your periodic table. 411 00:21:05,815 --> 00:21:08,184 This is where you get that information. 412 00:21:08,284 --> 00:21:12,255 OK, so we'll be building that up as we go. 413 00:21:12,355 --> 00:21:15,591 Well, let's say why do I need to count? 414 00:21:15,691 --> 00:21:18,327 Well, let's go back to answer our question now. 415 00:21:18,427 --> 00:21:20,062 That's the link. 416 00:21:20,162 --> 00:21:25,468 That number, Avogadro's constant links these atomic masses 417 00:21:25,568 --> 00:21:26,702 to grams. 418 00:21:26,802 --> 00:21:27,436 All right? 419 00:21:30,406 --> 00:21:31,774 Now I can answer the question. 420 00:21:31,874 --> 00:21:34,543 How many candle molecules burn in one minute? 421 00:21:34,644 --> 00:21:35,645 Well, let's do that. 422 00:21:35,745 --> 00:21:44,654 Because now I know that one mole of C25H52 423 00:21:44,754 --> 00:21:53,129 is something like 352.7 grams. 424 00:21:53,229 --> 00:21:54,430 How do I know that? 425 00:21:54,530 --> 00:21:58,801 Because I can look up what a mole 426 00:21:58,901 --> 00:22:01,837 weighs of carbon in here, how many grams. 427 00:22:01,937 --> 00:22:05,174 And I can look up how many grams of mole hydrogen weighs. 428 00:22:05,274 --> 00:22:08,077 And then I can multiply 25 and 52. 429 00:22:08,177 --> 00:22:09,712 And that's how many grams I get. 430 00:22:09,812 --> 00:22:12,048 One mole of it is that. 431 00:22:12,148 --> 00:22:13,816 Aha, the link is coming. 432 00:22:13,916 --> 00:22:14,650 The link is coming. 433 00:22:14,750 --> 00:22:15,618 It's very exciting. 434 00:22:19,121 --> 00:22:24,093 Because in a 12-hour candle, if it's 90 grams, 435 00:22:24,193 --> 00:22:31,901 so if I have a 90 gram candle, as I've said in the problem, 436 00:22:32,001 --> 00:22:41,677 then I know now that that is about 0.25 moles. 437 00:22:41,777 --> 00:22:43,813 Right, because of this. 438 00:22:43,913 --> 00:22:44,413 See that? 439 00:22:44,513 --> 00:22:46,015 90 over that. 440 00:22:46,115 --> 00:22:50,319 So now, I know how many moles of candle I've got. 441 00:22:50,419 --> 00:22:52,688 I know how many moles of candle I've got. 442 00:22:52,788 --> 00:22:57,626 But remember a mole is just a number. 443 00:22:57,727 --> 00:23:00,062 It's just a number. 444 00:23:00,162 --> 00:23:03,099 So this is how many moles of candle molecules I have. 445 00:23:03,199 --> 00:23:04,834 And OK. 446 00:23:04,934 --> 00:23:05,601 In one minute. 447 00:23:05,701 --> 00:23:06,869 It says in one minute. 448 00:23:06,969 --> 00:23:09,939 So in one minute-- 449 00:23:10,039 --> 00:23:12,274 well, OK, there's 60 minutes in an hour, 450 00:23:12,375 --> 00:23:15,778 and it's 12 hours, just a 720-minute candle. 451 00:23:15,878 --> 00:23:16,846 Right? 452 00:23:16,946 --> 00:23:21,417 So in one minute, 1/720 of that is what 453 00:23:21,517 --> 00:23:24,253 burns, if it lasts 12 hours. 454 00:23:24,353 --> 00:23:26,956 I'm just taking the information I was given. 455 00:23:27,056 --> 00:23:30,426 And I'm using the math of minutes and hours. 456 00:23:30,526 --> 00:23:33,396 1/720, OK. 457 00:23:33,496 --> 00:23:34,296 All right, good. 458 00:23:34,397 --> 00:23:38,000 So 1/720th of the candle burns. 459 00:23:38,100 --> 00:23:43,139 In one minute, 1/720 of the candle burns. 460 00:23:43,239 --> 00:23:47,309 And if the candle is that many moles, that's this many moles-- 461 00:23:47,410 --> 00:23:50,613 0.003. 462 00:23:50,713 --> 00:23:55,384 No, 0347 moles. 463 00:23:55,484 --> 00:23:56,752 Why did I do all that? 464 00:23:56,852 --> 00:23:59,622 Because I can now answer the question, cause of Avogadro's 465 00:23:59,722 --> 00:24:02,491 constant, because a mole is just a number. 466 00:24:02,591 --> 00:24:03,526 A mole is just a number. 467 00:24:03,626 --> 00:24:06,262 So if I've got that many moles, then I 468 00:24:06,362 --> 00:24:18,741 know that I've got 2 times 10 to the 20th molecules roughly. 469 00:24:18,841 --> 00:24:20,509 So I have been able to answer this question 470 00:24:20,609 --> 00:24:21,777 by going back and forth. 471 00:24:21,877 --> 00:24:22,812 [inaudible] 472 00:24:22,912 --> 00:24:25,281 I look here to get the grams per mole. 473 00:24:25,381 --> 00:24:28,584 I figured out how much candle I had. 474 00:24:28,684 --> 00:24:31,320 In grams, that gave me how many moles I have of candle. 475 00:24:31,420 --> 00:24:32,888 And then gave me the number-- 476 00:24:32,988 --> 00:24:34,156 back and forth, back and forth. 477 00:24:34,256 --> 00:24:35,524 That's what we do. 478 00:24:35,624 --> 00:24:40,229 Avogadro's constant gets us in and out of the atomic world. 479 00:24:40,329 --> 00:24:41,464 OK? 480 00:24:41,564 --> 00:24:42,832 And so we're going to practice that a little bit. 481 00:24:45,568 --> 00:24:49,538 And this gets me back to what we started on Wednesday. 482 00:24:49,638 --> 00:24:53,142 And I always like to give you guys advice if I can. 483 00:24:53,242 --> 00:24:54,643 And last time I mentioned, if you're 484 00:24:54,743 --> 00:24:57,146 on a date at a restaurant, ask them to give you, 485 00:24:57,246 --> 00:25:01,517 not a candle, but some C25H52 as a test for the quality 486 00:25:01,617 --> 00:25:02,284 of the restaurant. 487 00:25:02,384 --> 00:25:03,552 [laughter] 488 00:25:03,652 --> 00:25:07,089 Now, I'm asking you to do something else. 489 00:25:07,189 --> 00:25:07,857 It's noisy. 490 00:25:07,957 --> 00:25:09,124 You want to talk. 491 00:25:09,258 --> 00:25:09,959 Right? 492 00:25:10,059 --> 00:25:11,227 You go out on a first date. 493 00:25:11,327 --> 00:25:12,361 You're a little nervous. 494 00:25:12,461 --> 00:25:14,196 You want a quieter room. 495 00:25:14,296 --> 00:25:17,132 Ask them if there's a room where you can kind of shut the door 496 00:25:17,199 --> 00:25:18,501 and get that noise out. 497 00:25:18,601 --> 00:25:20,202 And it's quiet so you can talk. 498 00:25:20,302 --> 00:25:23,706 But now, you are armed with very important knowledge, 499 00:25:23,806 --> 00:25:26,208 because now, you know how much volume you 500 00:25:26,308 --> 00:25:28,677 have of air in the room and therefore, how much oxygen you 501 00:25:28,777 --> 00:25:29,178 have. 502 00:25:29,278 --> 00:25:31,747 [laughter] 503 00:25:31,847 --> 00:25:35,818 And if you light a candle, and you're taken 10 to the 2 times 504 00:25:35,918 --> 00:25:37,887 into 20 the molecules of candle out of the year, 505 00:25:37,987 --> 00:25:41,056 by the way, how many molecules of oxygen are you burning? 506 00:25:46,629 --> 00:25:50,332 Ah, how many molecules of oxygen? 507 00:25:50,432 --> 00:25:54,670 Ha, for at 38, balance-- 508 00:25:54,770 --> 00:25:57,873 38 times as many molecules. 509 00:25:57,973 --> 00:25:59,275 For each one of these that burns, 510 00:25:59,375 --> 00:26:06,715 you need 38 molecules of oxygen. So 38 times as many O2. 511 00:26:10,619 --> 00:26:14,356 Now, I don't know about you, but if I'm on this date, 512 00:26:14,456 --> 00:26:16,759 I'm looking it up. 513 00:26:16,859 --> 00:26:17,259 The human-- 514 00:26:17,359 --> 00:26:19,428 [laughter] 515 00:26:19,528 --> 00:26:25,434 --needs 1.9 grams of oxygen per minute. 516 00:26:30,072 --> 00:26:31,540 You need that. 517 00:26:31,640 --> 00:26:32,908 I mean, maybe it's variable. 518 00:26:33,008 --> 00:26:34,009 But you need roughly-- 519 00:26:34,109 --> 00:26:34,944 and there's two of you. 520 00:26:41,150 --> 00:26:51,126 0.4 grams of O2 is burned per minute. 521 00:26:54,363 --> 00:26:57,032 0 point-- who's going to win-- 522 00:26:57,132 --> 00:26:59,668 you or the candle? 523 00:26:59,768 --> 00:27:02,037 So you got to be just aware of this. 524 00:27:02,137 --> 00:27:08,310 And now look, This is kind of thing we can do now. 525 00:27:08,410 --> 00:27:09,745 And I'm not saying that everyone's 526 00:27:09,845 --> 00:27:11,580 going to understand this. 527 00:27:11,680 --> 00:27:14,450 You might not be with an MIT student. 528 00:27:14,550 --> 00:27:17,252 You might be with a student from some other school 529 00:27:17,353 --> 00:27:18,654 down the street. 530 00:27:18,754 --> 00:27:19,655 [laughter] 531 00:27:19,755 --> 00:27:24,526 All I want to say, be nice, be nice. 532 00:27:24,627 --> 00:27:26,929 It may not be their fault that they're where they are. 533 00:27:27,029 --> 00:27:28,197 [laughter] 534 00:27:28,297 --> 00:27:32,067 It may not be their fault. Go through this with them 535 00:27:32,167 --> 00:27:33,235 carefully, slowly. 536 00:27:33,335 --> 00:27:35,604 [laughter] 537 00:27:35,704 --> 00:27:38,707 Explain these concepts. 538 00:27:38,807 --> 00:27:41,076 And this gets me to the other topic of conversation 539 00:27:41,176 --> 00:27:42,645 that you can have. 540 00:27:42,745 --> 00:27:46,615 And this gets me to my why this matters moment for today. 541 00:27:46,715 --> 00:27:47,883 Why does this matter? 542 00:27:47,983 --> 00:27:50,853 Why does counting and thinking about how much of stuff 543 00:27:50,953 --> 00:27:55,057 you're using by using chemistry and moles? 544 00:27:55,157 --> 00:27:55,924 Why does that matter? 545 00:27:56,025 --> 00:27:58,661 Well, let's take an example. 546 00:27:58,761 --> 00:28:02,131 Let's take an example of nothing less than the number 547 00:28:02,231 --> 00:28:04,700 of humans on this planet. 548 00:28:04,800 --> 00:28:07,169 This is the population of humans. 549 00:28:07,269 --> 00:28:12,307 And you can see that it wasn't all that much until lately. 550 00:28:12,408 --> 00:28:14,810 But let's focus in on this part here. 551 00:28:14,910 --> 00:28:16,245 Let's focus in on that part there. 552 00:28:16,345 --> 00:28:17,079 Right. 553 00:28:17,179 --> 00:28:18,247 So that's billions of people. 554 00:28:18,347 --> 00:28:21,517 So if I zoom in on this, there's a change. 555 00:28:21,617 --> 00:28:22,451 Look at that. 556 00:28:22,551 --> 00:28:23,786 It's kind of going a little bit up. 557 00:28:23,886 --> 00:28:25,754 But now, it really kicks up. 558 00:28:25,854 --> 00:28:28,691 What happened during that time? 559 00:28:28,791 --> 00:28:34,129 What happened is a very important chemical reaction, 560 00:28:34,229 --> 00:28:38,300 became easy to do or a lot easier. 561 00:28:38,400 --> 00:28:39,768 OK? 562 00:28:39,868 --> 00:28:41,537 And the process that enabled that 563 00:28:41,637 --> 00:28:45,340 is called the Haber-Bosch process. 564 00:28:45,441 --> 00:28:49,878 But it is what allowed us to feed billions 565 00:28:49,978 --> 00:28:53,615 of people in a sustainable way. 566 00:28:53,716 --> 00:28:55,818 It's arguable whether we're doing that sustainably 567 00:28:55,918 --> 00:28:58,320 but in a way where we could actually produce enough-- 568 00:28:58,420 --> 00:28:59,488 enough what? 569 00:28:59,588 --> 00:29:00,823 Enough ammonia. 570 00:29:00,923 --> 00:29:06,462 And here's the deal you see, because plants need nitrogen 571 00:29:06,562 --> 00:29:08,464 to grow. 572 00:29:08,564 --> 00:29:09,965 Right? 573 00:29:10,065 --> 00:29:12,768 And there's 70% of the atmosphere is nitrogen. 574 00:29:12,868 --> 00:29:15,604 But it's useless, because it's N2. 575 00:29:15,704 --> 00:29:18,173 And N2 is one of the strongest bonds in nature. 576 00:29:18,273 --> 00:29:20,209 And plants can't break it. 577 00:29:20,309 --> 00:29:23,212 Now, we knew how to break it before. 578 00:29:23,312 --> 00:29:26,181 We knew how to do this before, right? 579 00:29:26,281 --> 00:29:28,150 This is called fixing-- 580 00:29:28,250 --> 00:29:35,357 fixing nitrogen. And the way it works is you go N2 plus h. 581 00:29:35,457 --> 00:29:39,528 This is a reaction, goes to NH3. 582 00:29:39,628 --> 00:29:40,863 What is wrong with this? 583 00:29:40,963 --> 00:29:41,864 [inaudible] 584 00:29:41,964 --> 00:29:44,466 It's not balanced. 585 00:29:44,566 --> 00:29:45,701 Thank you. 586 00:29:45,801 --> 00:29:50,539 Did anybody say, balancing is the same as mole ratio. 587 00:29:50,639 --> 00:29:54,209 Balancing and mole ratio's the same-- counting. 588 00:29:54,309 --> 00:29:55,410 Remember, we talk about that. 589 00:29:55,511 --> 00:29:57,112 But balancing is counting. 590 00:29:57,212 --> 00:29:58,847 So let's see-- oh, 2 here. 591 00:29:58,947 --> 00:30:01,917 OK, that helps me with the nitrogen. 592 00:30:02,017 --> 00:30:03,152 Oh, but this is H2. 593 00:30:03,252 --> 00:30:04,753 I meant to put that in the first place. 594 00:30:04,853 --> 00:30:07,189 And then so this is a 3. 595 00:30:07,289 --> 00:30:09,158 That reaction was known and doable. 596 00:30:09,291 --> 00:30:12,294 But it took tremendous amounts of energy. 597 00:30:12,394 --> 00:30:13,629 So it's very difficult to scale. 598 00:30:13,729 --> 00:30:16,632 And Haber-Bosch came up with a way using catalysis 599 00:30:16,732 --> 00:30:18,066 to do it at much lower temperatures. 600 00:30:18,167 --> 00:30:20,469 Catalysis is something we'll learn later in the semester. 601 00:30:23,338 --> 00:30:25,407 But how do we answer this question? 602 00:30:25,507 --> 00:30:26,475 What's my question? 603 00:30:26,575 --> 00:30:29,411 My question is how long can we keep going? 604 00:30:29,511 --> 00:30:34,082 50% of every protein you put in your body-- 605 00:30:34,183 --> 00:30:36,819 50% come from this-- 606 00:30:36,919 --> 00:30:40,022 comes from some plant that was grown using this process. 607 00:30:40,122 --> 00:30:42,157 That's how important it is. 608 00:30:42,257 --> 00:30:46,161 It's 500 million tons of nitrogen 609 00:30:46,261 --> 00:30:48,831 is made this way every year. 610 00:30:48,931 --> 00:30:50,799 Well, it's just counting. 611 00:30:50,899 --> 00:30:58,006 One mole of ammonia is 17 grams. 612 00:30:58,106 --> 00:30:59,508 Oh, we're doing the same thing. 613 00:30:59,608 --> 00:31:00,475 How did I know that? 614 00:31:00,576 --> 00:31:02,010 Periodic table. 615 00:31:02,110 --> 00:31:03,979 That's how I knew that. 616 00:31:04,079 --> 00:31:07,049 One mole-- if that many molecules of ammonia, 617 00:31:07,149 --> 00:31:08,383 I've got 17 grams of it. 618 00:31:14,323 --> 00:31:18,393 Let's say I just need to make the same amount of-- 619 00:31:18,493 --> 00:31:22,531 it says so times 10 to the 6 tons. 620 00:31:22,631 --> 00:31:29,538 I need that much tons of NH3 per year. 621 00:31:29,638 --> 00:31:31,006 That's our-- yeah, per year-- 622 00:31:31,106 --> 00:31:32,140 per year. 623 00:31:32,241 --> 00:31:35,143 OK, so that sets up my problem. 624 00:31:35,244 --> 00:31:37,212 I know how much I need. 625 00:31:37,312 --> 00:31:41,617 I know how many atoms we're talking about in one mole. 626 00:31:41,717 --> 00:31:45,821 Now, I can actually understand how many moles-- 627 00:31:45,921 --> 00:31:48,523 so I'm just going to not do the detailed math 628 00:31:48,624 --> 00:31:49,858 but how many moles I have. 629 00:31:49,958 --> 00:31:55,163 So I've got 30 times 10 to the 12th moles. 630 00:31:55,264 --> 00:32:03,739 This is how many moles I needed per year. 631 00:32:03,839 --> 00:32:06,008 How much do I have? 632 00:32:06,108 --> 00:32:07,542 Well, we know how much the atmosphere 633 00:32:07,643 --> 00:32:09,044 weighs-- it turns out. 634 00:32:09,144 --> 00:32:13,115 We know how much the atmosphere weighs. 635 00:32:13,215 --> 00:32:20,889 The mass of the atmosphere is something like 5 times 10 636 00:32:20,989 --> 00:32:23,191 to the 21st grams. 637 00:32:23,292 --> 00:32:35,637 And if I take 78% of that as my N2, so 78% is N2, 638 00:32:35,737 --> 00:32:39,574 then I can tell you that I've got-- 639 00:32:39,675 --> 00:32:50,385 let's see, 1.4 times 10 to the 20th moles of N2. 640 00:32:50,485 --> 00:32:52,020 That's how much I have available. 641 00:32:56,124 --> 00:32:57,259 OK? 642 00:32:57,359 --> 00:32:59,594 So if I keep on taking N2 out of the atmosphere, 643 00:32:59,695 --> 00:33:02,197 then I can now answer the question just like the candle. 644 00:33:02,297 --> 00:33:03,532 All right, how long do you have? 645 00:33:03,632 --> 00:33:05,334 I can answer the question, how long can we 646 00:33:05,434 --> 00:33:10,172 keep taking N2 out of the atmosphere 647 00:33:10,272 --> 00:33:13,775 and using Haber-Bosch, right? 648 00:33:13,875 --> 00:33:15,944 Oh, well, you would use the balanced reaction. 649 00:33:16,044 --> 00:33:17,479 So for every mole event do I take, 650 00:33:17,579 --> 00:33:19,348 I get two moles of ammonia. 651 00:33:19,448 --> 00:33:20,248 That's good. 652 00:33:20,349 --> 00:33:22,150 And you can work backwards. 653 00:33:22,250 --> 00:33:24,753 And you can learn that you're good. 654 00:33:24,853 --> 00:33:28,924 We're good for now. 655 00:33:29,024 --> 00:33:31,026 We have roughly 100 million years. 656 00:33:34,062 --> 00:33:34,463 OK? 657 00:33:39,868 --> 00:33:42,671 We have 100 million years that we could keep consuming. 658 00:33:42,771 --> 00:33:45,607 And then we'll run out of N2 in the atmosphere. 659 00:33:45,707 --> 00:33:47,376 How fun was that? 660 00:33:47,476 --> 00:33:49,411 OK, I love doing this. 661 00:33:49,511 --> 00:33:52,114 Now, when I get excited-- 662 00:33:52,214 --> 00:33:53,448 wow. 663 00:33:53,548 --> 00:33:56,651 Wait, before I get excited, what's the limiting reagent? 664 00:33:56,752 --> 00:33:58,086 [? add ?] enough N2. 665 00:33:58,186 --> 00:33:59,321 Is it N2? 666 00:33:59,421 --> 00:34:01,156 How do you know? 667 00:34:01,256 --> 00:34:01,957 How could you show? 668 00:34:02,057 --> 00:34:04,659 How can you prove? 669 00:34:04,760 --> 00:34:06,962 Limiting range, it means what runs out first? 670 00:34:07,062 --> 00:34:10,364 Well, oh, I'll just take H2 from the atmosphere, right? 671 00:34:10,465 --> 00:34:12,467 Na, uh. 672 00:34:12,567 --> 00:34:14,770 There's no H2 in the atmosphere. 673 00:34:14,870 --> 00:34:16,538 Where's the H2? 674 00:34:16,638 --> 00:34:18,907 Di da, it's over here-- 675 00:34:19,007 --> 00:34:20,007 H2O. 676 00:34:20,108 --> 00:34:21,176 It's in the oceans. 677 00:34:21,275 --> 00:34:22,577 How much H2O do I have? 678 00:34:22,677 --> 00:34:23,078 Well-- 679 00:34:23,178 --> 00:34:26,114 [laughter] 680 00:34:26,214 --> 00:34:28,583 It turns out you've got a lot. 681 00:34:28,683 --> 00:34:32,954 10 to the 23rd-ish moles of H2O, right? 682 00:34:33,054 --> 00:34:34,623 10 to the 23rd-ish moles. 683 00:34:34,723 --> 00:34:37,592 And so because of those coefficients of the reaction, 684 00:34:37,692 --> 00:34:40,228 you know exactly which one is going to run out first. 685 00:34:40,328 --> 00:34:43,065 You know it's N2, so your answer over there was correct. 686 00:34:43,165 --> 00:34:45,233 N2 is the limiting-- 687 00:34:45,333 --> 00:34:46,301 I love that little dance. 688 00:34:46,400 --> 00:34:47,735 I'm going to try to learn that. 689 00:34:47,835 --> 00:34:50,405 I'm going to learn that later. 690 00:34:50,505 --> 00:34:52,706 If you try this, you go 100 million years. 691 00:34:52,808 --> 00:34:56,043 You run out of N2-- plenty of H2 left. 692 00:34:56,143 --> 00:34:57,112 Let me read you. 693 00:34:57,212 --> 00:34:59,548 When I get excited, I didn't miss this. 694 00:34:59,648 --> 00:35:02,050 I like to throw stuff like T-shirts. 695 00:35:02,150 --> 00:35:06,521 Now, the thing is these T-shirts are not-- 696 00:35:06,621 --> 00:35:08,323 [laughter] 697 00:35:08,423 --> 00:35:10,192 Now, and I go like this. 698 00:35:10,292 --> 00:35:11,993 [laughter] 699 00:35:12,094 --> 00:35:17,499 And then I go all the way-- ahh, to the back, all the way 700 00:35:17,599 --> 00:35:21,670 up there, all the way up there. 701 00:35:21,770 --> 00:35:23,939 All right. 702 00:35:24,039 --> 00:35:30,579 OK, now look-- why do I throw T-shirts? 703 00:35:30,679 --> 00:35:31,613 I have no idea. 704 00:35:31,713 --> 00:35:33,748 [laughter] 705 00:35:33,849 --> 00:35:37,686 Sometimes things are just better left unknown. 706 00:35:37,786 --> 00:35:44,626 But please, I'll throw T-shirts 34 more times. 707 00:35:44,726 --> 00:35:46,561 Every lecture, I'm going to throw some T-shirts 708 00:35:46,661 --> 00:35:47,829 when I get a little excited. 709 00:35:47,929 --> 00:35:51,833 And please, if you get a T-shirt a second time, share. 710 00:35:51,933 --> 00:35:54,769 Right, don't take it-- give it to somebody-- trade. 711 00:35:54,870 --> 00:35:55,403 Right? 712 00:35:55,504 --> 00:35:56,705 Sharing is caring. 713 00:35:56,805 --> 00:35:57,506 Now, where were we. 714 00:35:57,606 --> 00:35:59,975 OK, now, here we are. 715 00:36:00,075 --> 00:36:01,877 We got to build this? 716 00:36:01,977 --> 00:36:08,250 Here's the thing-- in 1669, there are only 12 elements 717 00:36:08,350 --> 00:36:09,518 known. 718 00:36:09,618 --> 00:36:11,586 But yeah, I hope I've given you a sense. 719 00:36:11,686 --> 00:36:14,356 All these people and many more, I haven't even named. 720 00:36:14,456 --> 00:36:18,260 We're working on discovering new ones. 721 00:36:18,360 --> 00:36:23,398 By 1799, we had 34. 722 00:36:23,498 --> 00:36:25,600 Dalton and I mentioned had a table of 36, 723 00:36:25,700 --> 00:36:27,202 and they kept going. 724 00:36:27,302 --> 00:36:31,373 And as we got more and more elements, a lot of people 725 00:36:31,473 --> 00:36:34,276 were wondering, how do we organize these? 726 00:36:34,376 --> 00:36:36,011 How do we organize these? 727 00:36:36,111 --> 00:36:37,679 And are there patterns? 728 00:36:37,779 --> 00:36:39,881 Are there patterns, right? 729 00:36:39,981 --> 00:36:41,816 That became a hot question. 730 00:36:41,917 --> 00:36:44,319 Yes, they still wanted to smash and break and burn and make 731 00:36:44,419 --> 00:36:45,954 new, discover new things. 732 00:36:46,054 --> 00:36:48,590 But they also wanted to know what it all means. 733 00:36:48,690 --> 00:36:51,560 It wasn't just like a few-- it was a lot. 734 00:36:51,660 --> 00:36:53,328 And so they started looking for patterns. 735 00:36:53,428 --> 00:36:55,997 And one of the first people was Dobereiner, 736 00:36:56,097 --> 00:37:00,468 who came up with what he called the Law of Triads, which was 737 00:37:00,569 --> 00:37:01,903 a law that worked three times. 738 00:37:02,003 --> 00:37:05,574 [laughs] But what he found-- 739 00:37:05,674 --> 00:37:08,043 [inaudible],, everybody was arranging these elements 740 00:37:08,143 --> 00:37:08,877 in different ways. 741 00:37:08,977 --> 00:37:11,146 [inaudible] arrange it by mass. 742 00:37:11,246 --> 00:37:13,582 No, arrange it by something else. 743 00:37:13,682 --> 00:37:16,952 And he found that if you listed him kind of by mass-ish, 744 00:37:17,052 --> 00:37:20,422 then the middle atom of the three 745 00:37:20,522 --> 00:37:23,892 would weigh exactly half or roughly half of these two. 746 00:37:23,992 --> 00:37:25,627 That was cool for three times. 747 00:37:28,363 --> 00:37:31,800 OK, Newlands did something really important. 748 00:37:31,900 --> 00:37:35,604 Well, first of all, he loved music. 749 00:37:35,704 --> 00:37:39,107 And he arranged elements like this and again, kind 750 00:37:39,207 --> 00:37:40,508 of by mass. 751 00:37:40,609 --> 00:37:44,212 And he noticed that there were repeating patterns every eight. 752 00:37:44,312 --> 00:37:46,514 Now, unlike a lot of triads, this was really important, 753 00:37:46,615 --> 00:37:48,116 because the Law of Triads, you said, 754 00:37:48,216 --> 00:37:49,584 look, I can take these three. 755 00:37:49,684 --> 00:37:50,919 I can take those three. 756 00:37:51,019 --> 00:37:54,623 That's kind of cool, but it wasn't periodic. 757 00:37:54,723 --> 00:37:57,259 It didn't happen these three then, the next three. 758 00:37:57,359 --> 00:38:00,996 And whereas the Newlands, it was periodic. 759 00:38:01,096 --> 00:38:04,933 And it sort of also only worked for 2 and 1/2 runs. 760 00:38:05,033 --> 00:38:06,601 The Law of Octaves-- 761 00:38:06,701 --> 00:38:08,270 he called it the Law of Octaves. 762 00:38:08,370 --> 00:38:10,472 Oh, this was the time to look for patterns. 763 00:38:10,572 --> 00:38:14,142 And many people took a stab at it. 764 00:38:14,242 --> 00:38:17,545 Julius Meyer made some really important contributions 765 00:38:17,646 --> 00:38:21,049 in measuring the molar volume by knowing the densities 766 00:38:21,149 --> 00:38:22,951 and finding patterns. 767 00:38:23,051 --> 00:38:25,587 they were looking for periodicity. 768 00:38:25,687 --> 00:38:27,389 But as many of you may already know, 769 00:38:27,489 --> 00:38:34,596 it was Mendeleev who figured out what needed to be done. 770 00:38:34,696 --> 00:38:39,067 And what he figured out was absolutely critical. 771 00:38:39,167 --> 00:38:40,535 Let's go to the middle. 772 00:38:43,838 --> 00:38:45,240 And notice, he's listing them-- 773 00:38:45,340 --> 00:38:47,909 OK, he didn't know whether to put it this way or sideways 774 00:38:48,009 --> 00:38:50,011 or what. 775 00:38:50,111 --> 00:38:53,248 This is oriented differently than what we do today. 776 00:38:53,348 --> 00:38:54,449 But it's OK. 777 00:38:54,549 --> 00:38:56,751 He's just listing them and looking for patterns. 778 00:38:56,851 --> 00:39:00,388 But what Mendeleev did that were so critical-- 779 00:39:00,488 --> 00:39:04,759 what he did that was so important 780 00:39:04,859 --> 00:39:08,630 is that he organized them. 781 00:39:08,730 --> 00:39:14,369 So Mendeleev-- Mendeleev-- 782 00:39:14,469 --> 00:39:19,107 he had, at the time, this was-- let's see 1869. 783 00:39:19,207 --> 00:39:21,176 He had 63 elements. 784 00:39:23,878 --> 00:39:27,582 And he called this a periodic system. 785 00:39:27,682 --> 00:39:35,457 And the critical piece is he arranged them by mass. 786 00:39:38,193 --> 00:39:41,830 And this is so important-- properties. 787 00:39:46,501 --> 00:39:52,974 He really believed that the periodicity was the driver, 788 00:39:53,074 --> 00:39:57,812 and that the properties were critical in this organization-- 789 00:39:57,912 --> 00:40:00,048 the properties and the mass. 790 00:40:00,148 --> 00:40:00,548 Right? 791 00:40:04,386 --> 00:40:11,092 He was so certain that you had to take them both into account 792 00:40:11,192 --> 00:40:14,963 that he actually left gaps. 793 00:40:15,063 --> 00:40:17,499 That was new. 794 00:40:17,599 --> 00:40:20,735 At least for this many elements and arranging it this way, 795 00:40:20,835 --> 00:40:21,836 that was different. 796 00:40:21,936 --> 00:40:23,738 And so like, for example, look at this. 797 00:40:23,838 --> 00:40:29,644 Over here, so here you have aluminum, silicon. 798 00:40:29,744 --> 00:40:30,612 And you know what else? 799 00:40:30,712 --> 00:40:31,780 Uncover this, so you can it. 800 00:40:31,880 --> 00:40:33,648 Oh, zinc-- OK, zinc. 801 00:40:33,748 --> 00:40:34,849 Right, arsenic. 802 00:40:34,949 --> 00:40:38,553 But he said, no, don't just put this next to zinc 803 00:40:38,653 --> 00:40:40,755 because of the properties. 804 00:40:40,855 --> 00:40:42,390 This doesn't have the right properties. 805 00:40:42,490 --> 00:40:44,492 This should be more like phosphorus. 806 00:40:44,592 --> 00:40:45,693 So we're going to leave gaps. 807 00:40:48,830 --> 00:40:51,933 And this is really important-- he predicted the properties 808 00:40:52,033 --> 00:40:53,334 of those missing elements. 809 00:40:53,435 --> 00:40:56,571 So if you call this, for example, with silicon, 810 00:40:56,671 --> 00:40:58,807 we know this is germanium. 811 00:40:58,907 --> 00:41:00,141 We know that now. 812 00:41:00,241 --> 00:41:01,876 But back then, no one had smashed and burned and broken 813 00:41:01,976 --> 00:41:05,346 enough stuff to find germanium. 814 00:41:05,447 --> 00:41:07,348 So he said, well, we can predict it. 815 00:41:07,449 --> 00:41:10,885 Because it comes here in this table in this organization, 816 00:41:10,985 --> 00:41:13,455 therefore, it must have properties 817 00:41:13,555 --> 00:41:18,560 similar to other elements in that column. 818 00:41:18,660 --> 00:41:19,861 And he called it eco-silicon. 819 00:41:19,961 --> 00:41:21,729 Eco just means one next, right? 820 00:41:21,830 --> 00:41:24,232 And so these are predictions by Mendeleev-- predictions 821 00:41:24,332 --> 00:41:26,334 of the properties of this missing element. 822 00:41:26,434 --> 00:41:29,838 And here's what you get when you actually find germanium years 823 00:41:29,938 --> 00:41:30,772 and years later. 824 00:41:30,872 --> 00:41:31,940 And you measure those properties. 825 00:41:32,040 --> 00:41:33,107 And look at that-- 826 00:41:33,208 --> 00:41:35,009 it's incredible. 827 00:41:35,109 --> 00:41:36,144 Right? 828 00:41:36,244 --> 00:41:39,481 Thank you for that wow because I felt it too. 829 00:41:39,581 --> 00:41:40,582 Any more T-shirts? 830 00:41:40,682 --> 00:41:43,651 Aw, I felt the wow, and it made me excited. 831 00:41:43,751 --> 00:41:46,154 [laughter] 832 00:41:46,254 --> 00:41:48,156 All right. 833 00:41:48,256 --> 00:41:48,990 This is a big deal. 834 00:41:49,090 --> 00:41:50,892 You go back to here-- 835 00:41:50,992 --> 00:41:54,596 iodine and tellurium-- no, I'm not 836 00:41:54,696 --> 00:41:56,364 going to give you the mass ordering, 837 00:41:56,464 --> 00:41:58,500 because it doesn't make sense in terms of property. 838 00:41:58,566 --> 00:42:01,636 So I'm going to keep the mass the other way, even though this 839 00:42:01,736 --> 00:42:03,872 has a higher mass, look at that question mark. 840 00:42:03,972 --> 00:42:07,275 I'm still going to put it before because it makes more sense. 841 00:42:07,375 --> 00:42:11,212 That's what Mendeleev did, and it was absolutely critical. 842 00:42:11,312 --> 00:42:14,482 It really brings us to the current system that we use. 843 00:42:14,582 --> 00:42:16,684 So this is now the periodic table. 844 00:42:16,784 --> 00:42:21,356 Our periodic table today is based Mendeleev's organization. 845 00:42:21,456 --> 00:42:24,325 And we're going to be spending a lot of time with it. 846 00:42:24,425 --> 00:42:26,160 So we're not going to go through everything. 847 00:42:26,261 --> 00:42:27,595 But a couple of things. 848 00:42:27,695 --> 00:42:30,031 First of all, there's a key. 849 00:42:30,131 --> 00:42:31,733 That's the key to the table. 850 00:42:31,833 --> 00:42:35,336 If a table doesn't have the key, don't use it. 851 00:42:35,436 --> 00:42:37,138 It should have a key. 852 00:42:37,238 --> 00:42:41,175 And so, for example, oh, look at that number. 853 00:42:41,276 --> 00:42:42,210 That looks nice. 854 00:42:42,310 --> 00:42:43,444 Right? 855 00:42:43,545 --> 00:42:46,548 That's the AMU or the grams per mole which we now 856 00:42:46,648 --> 00:42:48,016 know are equivalent-- 857 00:42:48,116 --> 00:42:51,052 not equivalent but relatable. 858 00:42:51,152 --> 00:42:53,755 You have a mole, that's how many grams you have. 859 00:42:53,855 --> 00:42:56,291 Or if you have one atom, that's how many AMU's you have, 860 00:42:56,391 --> 00:42:57,258 right there. 861 00:42:57,358 --> 00:42:59,794 The key tells you what things are. 862 00:42:59,894 --> 00:43:01,563 Right? 863 00:43:01,663 --> 00:43:05,300 Now, if you have a more complicated one, don't panic. 864 00:43:05,400 --> 00:43:06,367 Here's yours. 865 00:43:06,467 --> 00:43:08,803 This is your periodic table. 866 00:43:08,903 --> 00:43:10,772 Ha, look at this. 867 00:43:10,872 --> 00:43:13,441 It's all in the key. 868 00:43:13,541 --> 00:43:17,445 There's a lot more information in here then in the basic ones. 869 00:43:17,545 --> 00:43:18,580 But it's all in the key. 870 00:43:18,680 --> 00:43:19,881 It's all described in the key. 871 00:43:19,981 --> 00:43:23,051 And the key may be different on the front and the back. 872 00:43:23,151 --> 00:43:25,887 There may be different properties included. 873 00:43:25,987 --> 00:43:26,955 But it's all in the key. 874 00:43:27,055 --> 00:43:28,022 And look at it. 875 00:43:28,122 --> 00:43:29,657 Some of these we know like the weight-- 876 00:43:29,757 --> 00:43:31,960 atomic weight-- that's what we've been talking about. 877 00:43:32,060 --> 00:43:34,128 Melting point sounds kind of obvious-- boiling point 878 00:43:34,228 --> 00:43:35,496 density. 879 00:43:35,597 --> 00:43:37,365 And then you get to these other things-- electronegativity, 880 00:43:37,465 --> 00:43:38,666 first ionization. 881 00:43:38,766 --> 00:43:40,835 All these things, what are they? 882 00:43:40,935 --> 00:43:44,939 We will find out literally next week, all right, 883 00:43:45,039 --> 00:43:48,042 as we build up our understanding of the atom. 884 00:43:48,142 --> 00:43:49,177 But it's all on the key. 885 00:43:49,277 --> 00:43:52,447 Now, this is so important that I really 886 00:43:52,547 --> 00:43:58,319 ask you with passion to carry it with you everywhere you go. 887 00:43:58,419 --> 00:44:00,521 I really do, because you never know. 888 00:44:00,622 --> 00:44:02,323 Remember the restaurant example. 889 00:44:02,423 --> 00:44:04,826 You never know when you need it. 890 00:44:04,926 --> 00:44:06,027 You never know. 891 00:44:06,127 --> 00:44:08,262 And, in fact, you can send me pictures. 892 00:44:08,363 --> 00:44:08,963 Students do this. 893 00:44:09,063 --> 00:44:09,964 I love it. 894 00:44:10,064 --> 00:44:11,432 You don't have to send me pictures. 895 00:44:11,532 --> 00:44:14,202 You can just post it on your feed or whatever it's called. 896 00:44:14,302 --> 00:44:15,203 [inaudible] 897 00:44:15,303 --> 00:44:16,004 What's it called? 898 00:44:16,104 --> 00:44:19,540 I don't know-- a thing. 899 00:44:19,641 --> 00:44:21,376 So they took it all the way up to Dartmouth, 900 00:44:21,476 --> 00:44:23,611 because there were some people up there apparently that needed 901 00:44:23,711 --> 00:44:24,679 help with their chemistry. 902 00:44:24,779 --> 00:44:26,347 [laughter] 903 00:44:26,447 --> 00:44:29,817 Here we are at a restaurant, looking at the periodic table. 904 00:44:29,917 --> 00:44:30,918 Here's another. 905 00:44:31,019 --> 00:44:32,787 It's a good thing to have at a restaurant. 906 00:44:32,887 --> 00:44:34,756 You never know. 907 00:44:34,856 --> 00:44:36,591 Here it is again. 908 00:44:36,691 --> 00:44:38,292 Look at how happy they are. 909 00:44:38,393 --> 00:44:40,428 Look at that, right? 910 00:44:40,528 --> 00:44:41,796 They're really getting into it. 911 00:44:41,896 --> 00:44:47,802 They're really getting into it here, teaching family members 912 00:44:47,902 --> 00:44:50,238 about this or being proud of it with the whole family. 913 00:44:50,338 --> 00:44:52,974 [laughter] 914 00:44:53,074 --> 00:44:55,443 Take it with you. 915 00:44:55,543 --> 00:44:57,311 It'll come in handy no matter what. 916 00:44:57,412 --> 00:44:59,814 Here it is under a Christmas tree. 917 00:44:59,914 --> 00:45:01,049 Right? 918 00:45:01,149 --> 00:45:02,917 It's in here somewhere. 919 00:45:03,017 --> 00:45:04,118 And there it is. 920 00:45:04,218 --> 00:45:07,288 And look, even if you're dressing up for a theater, 921 00:45:07,388 --> 00:45:08,956 it's going to be important. 922 00:45:09,057 --> 00:45:11,726 OK, now, this is the one I want to get to-- 923 00:45:11,826 --> 00:45:13,261 OK, even if you're a little tired. 924 00:45:13,361 --> 00:45:14,762 It's going to be what comforts you. 925 00:45:14,862 --> 00:45:17,665 I think it's being used as a pillow. 926 00:45:17,765 --> 00:45:20,702 That's OK, it's comfortable. 927 00:45:20,802 --> 00:45:21,235 Look at this. 928 00:45:21,335 --> 00:45:24,739 [laughter] 929 00:45:26,340 --> 00:45:27,575 Right? 930 00:45:27,675 --> 00:45:28,910 Right? 931 00:45:29,010 --> 00:45:32,580 You know even at the dance club, even at the dance club, 932 00:45:32,680 --> 00:45:33,948 oh, I see that. 933 00:45:34,048 --> 00:45:35,083 You might need this. 934 00:45:35,183 --> 00:45:36,884 You don't know. 935 00:45:36,984 --> 00:45:39,087 You don't know. 936 00:45:39,187 --> 00:45:40,655 Look at how happy he is. 937 00:45:40,755 --> 00:45:42,056 [laughter] 938 00:45:42,156 --> 00:45:46,527 Look at that, because he has this. 939 00:45:46,627 --> 00:45:50,431 Take it with you everywhere you go. 940 00:45:50,531 --> 00:45:52,633 Now, there's a bunch of things about this table 941 00:45:52,734 --> 00:45:55,236 that we'll be talking about. 942 00:45:55,336 --> 00:45:56,204 We just built it up. 943 00:45:59,140 --> 00:46:01,375 The first things is just some nomenclature. 944 00:46:01,476 --> 00:46:03,244 Right, just how do we name things? 945 00:46:03,344 --> 00:46:07,248 We name things that the rose, we call them periods, 946 00:46:07,348 --> 00:46:08,683 and there's seven of them. 947 00:46:08,783 --> 00:46:10,818 The cones, we call them groups, and there's 948 00:46:10,918 --> 00:46:14,355 18 of them in the way we organize, in the way 949 00:46:14,455 --> 00:46:16,758 we present it, right? 950 00:46:16,891 --> 00:46:18,426 But there's something kind of important 951 00:46:18,526 --> 00:46:21,529 that happens here which is that these rows down here are 952 00:46:21,629 --> 00:46:25,633 actually 14 elements longer. 953 00:46:25,733 --> 00:46:28,136 So right, so this is 18 across. 954 00:46:28,236 --> 00:46:30,705 But these guys fit in right here. 955 00:46:30,805 --> 00:46:32,039 They go right there. 956 00:46:32,140 --> 00:46:33,374 Right? 957 00:46:33,474 --> 00:46:36,511 These are called the lanthanides because that's lanthanum-- 958 00:46:36,611 --> 00:46:37,779 innovative naming. 959 00:46:37,879 --> 00:46:39,447 These are called the actinides. 960 00:46:39,547 --> 00:46:40,248 OK. 961 00:46:40,348 --> 00:46:43,284 They go in there in between. 962 00:46:43,384 --> 00:46:44,786 Why don't we just put it all there? 963 00:46:44,886 --> 00:46:46,020 Well, you can. 964 00:46:46,120 --> 00:46:49,457 But then you got the bottom rows are 34. 965 00:46:49,557 --> 00:46:50,291 Right? 966 00:46:50,391 --> 00:46:51,425 And then the next one's up. 967 00:46:51,526 --> 00:46:53,060 There's only two rows in the periodic table 968 00:46:53,161 --> 00:46:55,263 that are actually 18. 969 00:46:55,363 --> 00:46:57,932 Then because then you got 18 here. 970 00:46:58,032 --> 00:46:59,801 And then these are eight. 971 00:46:59,901 --> 00:47:01,135 And then you got two up top. 972 00:47:01,235 --> 00:47:02,737 Now, why? 973 00:47:02,837 --> 00:47:05,306 That we will understand when we understand the atom 974 00:47:05,406 --> 00:47:07,108 a little better next week. 975 00:47:07,208 --> 00:47:08,476 OK? 976 00:47:08,576 --> 00:47:10,244 But for now, I just want to call your attention that these 977 00:47:10,344 --> 00:47:11,412 are the names that we use. 978 00:47:11,512 --> 00:47:13,447 And those top ones are called mean group. 979 00:47:13,548 --> 00:47:15,917 These ones are transition elements. 980 00:47:16,017 --> 00:47:17,018 You have alkalines here. 981 00:47:17,118 --> 00:47:19,887 You have lanthanides, actinides. 982 00:47:19,987 --> 00:47:22,223 These are the names that we give these regions that 983 00:47:22,323 --> 00:47:26,427 get more clear when we know what electrons are. 984 00:47:26,527 --> 00:47:30,364 And I think I'll tell you just the last bits 985 00:47:30,464 --> 00:47:33,100 about just a couple more observations 986 00:47:33,201 --> 00:47:35,736 about the periodic table, I think, 987 00:47:35,837 --> 00:47:39,740 when we start our lecture on Monday since it's 11:54. 988 00:47:39,841 --> 00:47:42,610 And as promised, I want to let you guys out right on time 989 00:47:42,710 --> 00:47:43,711 every lecture. 990 00:47:43,811 --> 00:47:46,614 Have a fantastic weekend and see you Monday.