1 00:00:00,000 --> 00:00:00,680 2 00:00:00,680 --> 00:00:03,480 We now have a respectable understanding of the periodic 3 00:00:03,480 --> 00:00:06,839 table itself and the atoms in them. 4 00:00:06,839 --> 00:00:10,070 And now we're ready to deal with molecules themselves. 5 00:00:10,070 --> 00:00:12,080 And to deal with molecules, we have to have some way of 6 00:00:12,080 --> 00:00:12,689 representing them. 7 00:00:12,689 --> 00:00:14,379 And you represent them with formulas. 8 00:00:14,380 --> 00:00:16,690 And there's two major-- actually, three major ways to 9 00:00:16,690 --> 00:00:17,650 represent a molecule. 10 00:00:17,649 --> 00:00:19,134 One is the molecular formula. 11 00:00:19,135 --> 00:00:28,230 12 00:00:28,230 --> 00:00:29,929 And the other is the empirical formula. 13 00:00:29,929 --> 00:00:32,728 And I'll do it in a different color to differentiate it. 14 00:00:32,728 --> 00:00:39,350 15 00:00:39,350 --> 00:00:41,609 And the difference is, well, let's just talk about what the 16 00:00:41,609 --> 00:00:42,659 word empirical means. 17 00:00:42,659 --> 00:00:45,119 I remember when I first took chemistry the teacher kept 18 00:00:45,119 --> 00:00:46,079 using the word empirical. 19 00:00:46,079 --> 00:00:48,390 Well, what does empirical really mean? 20 00:00:48,390 --> 00:00:51,310 I clearly did not have a very deep vocabulary. 21 00:00:51,310 --> 00:00:52,719 I forgot what age I was. 22 00:00:52,719 --> 00:00:58,469 But it means achieved through observation or experiment, or 23 00:00:58,469 --> 00:00:59,780 based on experience. 24 00:00:59,780 --> 00:01:04,180 So if someone said that they empirically figured out x, y, 25 00:01:04,180 --> 00:01:06,300 or z, it means that they figured it out through an 26 00:01:06,299 --> 00:01:08,149 experiment or they observed it. 27 00:01:08,150 --> 00:01:11,440 The molecular formula is essentially the actual number 28 00:01:11,439 --> 00:01:13,810 of atoms in that molecule. 29 00:01:13,810 --> 00:01:14,790 Let me show you what I'm talking about. 30 00:01:14,790 --> 00:01:18,330 So the empirical formula tells you what people have observed. 31 00:01:18,329 --> 00:01:20,730 Maybe before they even knew that there was such a thing as 32 00:01:20,730 --> 00:01:24,620 atoms, what they would have observed is the ratio of the 33 00:01:24,620 --> 00:01:26,910 atoms to one another in a molecule without knowing in 34 00:01:26,909 --> 00:01:29,500 the exact molecule how many of that atom there are. 35 00:01:29,500 --> 00:01:31,329 Let me show you what I'm talking about. 36 00:01:31,329 --> 00:01:42,789 So if I were to give you, I don't know, a benzene, the 37 00:01:42,790 --> 00:01:47,240 molecular formula of benzene, you have 6 carbon atoms and 38 00:01:47,239 --> 00:01:53,239 you have 6 hydrogen atoms. Now, if you were some chemist 39 00:01:53,239 --> 00:01:56,709 in the 1800's and you didn't know about the actual atoms, 40 00:01:56,709 --> 00:01:59,279 but if you had a big bag of benzene and you were to 41 00:01:59,280 --> 00:02:03,359 measure the ratio of the carbon to the hydrogen that 42 00:02:03,359 --> 00:02:05,870 you had in that bag, you would find out that for every one 43 00:02:05,870 --> 00:02:08,560 carbon you have one hydrogen. 44 00:02:08,560 --> 00:02:11,400 So your empirical formula is the ratio of the two. 45 00:02:11,400 --> 00:02:14,060 You don't know that each atom actually has 6 of these, but 46 00:02:14,060 --> 00:02:16,479 you know that for every carbon, there's a hydrogen. 47 00:02:16,479 --> 00:02:18,149 And for every hydrogen there's a carbon. 48 00:02:18,150 --> 00:02:21,030 And the way to go back, you can go from the molecular 49 00:02:21,030 --> 00:02:23,159 formula to the empirical formula very easily. 50 00:02:23,159 --> 00:02:27,870 You just find the greatest common divisor of the number 51 00:02:27,870 --> 00:02:29,640 of atoms in the molecule. 52 00:02:29,639 --> 00:02:32,569 So the greatest common divisor is six, and six is obviously 53 00:02:32,569 --> 00:02:34,590 six, you divide both of these by six and you get the 54 00:02:34,590 --> 00:02:35,710 empirical formula. 55 00:02:35,710 --> 00:02:36,730 It's not easy. 56 00:02:36,729 --> 00:02:39,090 You pretty much can't go back from the empirical formula to 57 00:02:39,090 --> 00:02:39,879 the molecular formula. 58 00:02:39,879 --> 00:02:41,289 You've lost information. 59 00:02:41,289 --> 00:02:43,299 I don't know whether this was C6H6. 60 00:02:43,300 --> 00:02:44,870 Was it C2H2? 61 00:02:44,870 --> 00:02:46,189 You just don't know. 62 00:02:46,189 --> 00:02:48,069 And I mentioned right at the beginning of the video that 63 00:02:48,069 --> 00:02:51,750 there's a third way to represent molecules. 64 00:02:51,750 --> 00:02:54,099 And that's the structural formula. 65 00:02:54,099 --> 00:02:55,879 And we'll do that, off and on, and we've already done it a 66 00:02:55,879 --> 00:02:56,719 little bit. 67 00:02:56,719 --> 00:02:57,250 Let me show you. 68 00:02:57,250 --> 00:02:59,759 The structural formula for benzene would actually say how 69 00:02:59,759 --> 00:03:02,489 the molecular formula atoms are configured. 70 00:03:02,490 --> 00:03:05,469 So benzene in particular is very interesting. 71 00:03:05,469 --> 00:03:06,270 It looks like this. 72 00:03:06,270 --> 00:03:08,290 It's often drawn like this. 73 00:03:08,289 --> 00:03:11,219 And you'll see this a lot when you take organic chemistry. 74 00:03:11,219 --> 00:03:15,379 But it looks like a little hexagon, where the vertices of 75 00:03:15,379 --> 00:03:18,310 the hexagon are carbon atoms. So let me draw the carbon 76 00:03:18,310 --> 00:03:19,000 atoms in yellow. 77 00:03:19,000 --> 00:03:22,719 So this is carbon, carbon, carbon, 78 00:03:22,719 --> 00:03:26,729 carbon, carbon, carbon. 79 00:03:26,729 --> 00:03:30,689 They have double bonds, every other carbon. 80 00:03:30,689 --> 00:03:31,919 Double bonds. 81 00:03:31,919 --> 00:03:36,199 And then they have single bonds to hydrogen. 82 00:03:36,199 --> 00:03:38,074 Let me just do the hydrogen in another color. 83 00:03:38,074 --> 00:03:41,479 84 00:03:41,479 --> 00:03:43,369 Let me do it in magenta. 85 00:03:43,370 --> 00:03:44,620 Hydrogen. 86 00:03:44,620 --> 00:03:50,800 87 00:03:50,800 --> 00:03:53,450 And obviously, the structural formula gives you the most 88 00:03:53,449 --> 00:03:54,939 information. 89 00:03:54,939 --> 00:03:55,199 Right? 90 00:03:55,199 --> 00:03:57,269 Then you can start to think about, gee, how will this 91 00:03:57,270 --> 00:03:58,890 interact with other things? 92 00:03:58,889 --> 00:04:01,309 While the molecular formula just tells you what's in the 93 00:04:01,310 --> 00:04:03,310 molecule, the empirical formula really gives you the 94 00:04:03,310 --> 00:04:04,469 least information. 95 00:04:04,469 --> 00:04:06,300 It just tells you the ratio of the different 96 00:04:06,300 --> 00:04:08,890 items in the molecule. 97 00:04:08,889 --> 00:04:12,419 Structural formula. 98 00:04:12,419 --> 00:04:14,389 Let's do a couple more. 99 00:04:14,389 --> 00:04:18,269 OK, what if we're dealing with, let's say we're dealing 100 00:04:18,269 --> 00:04:20,250 with water. 101 00:04:20,250 --> 00:04:23,279 I think you know the molecular formula for water. 102 00:04:23,279 --> 00:04:25,869 H2O. 103 00:04:25,870 --> 00:04:28,939 Now what would be the empirical formula for this? 104 00:04:28,939 --> 00:04:31,509 Well we want to know the ratio, so for every oxygen 105 00:04:31,509 --> 00:04:32,389 there's two hydrogens. 106 00:04:32,389 --> 00:04:34,000 Or I guess you could say for every hydrogen 107 00:04:34,000 --> 00:04:35,899 there's a half of oxygen. 108 00:04:35,899 --> 00:04:37,229 So you can't reduce this. 109 00:04:37,230 --> 00:04:42,280 If I wrote this as H2O1, what's the greatest common 110 00:04:42,279 --> 00:04:44,489 divisor of 2 and 1? 111 00:04:44,490 --> 00:04:46,480 Well, it's 1, so you just have to divide them by 1. 112 00:04:46,480 --> 00:04:51,410 So in this case, the empirical and the molecular formula are 113 00:04:51,410 --> 00:04:52,760 the exact same thing. 114 00:04:52,759 --> 00:04:54,389 It's H2O. 115 00:04:54,389 --> 00:04:55,569 What about sulfur? 116 00:04:55,569 --> 00:05:00,939 And an interesting molecule, because obviously, 117 00:05:00,939 --> 00:05:03,629 it's just one atom. 118 00:05:03,629 --> 00:05:04,560 Sulfur. 119 00:05:04,560 --> 00:05:08,449 Sorry, no, I'm spelling it wrong. 120 00:05:08,449 --> 00:05:09,620 No. 121 00:05:09,620 --> 00:05:13,660 No, it's not a p h, it's f. 122 00:05:13,660 --> 00:05:16,460 Clearly, I shouldn't be making spelling videos. 123 00:05:16,459 --> 00:05:17,709 So sulfur. 124 00:05:17,709 --> 00:05:23,120 125 00:05:23,120 --> 00:05:26,790 So the molecular formula S8. 126 00:05:26,790 --> 00:05:28,420 So it forms this neat kind of 127 00:05:28,420 --> 00:05:32,270 octagon-looking chain of sulfurs. 128 00:05:32,269 --> 00:05:34,120 And if I were to draw that, you would see that. 129 00:05:34,120 --> 00:05:36,490 And you could look it up on Wikipedia, if you like. 130 00:05:36,490 --> 00:05:39,319 But its empirical formula, if you had just a bag of sulfur, 131 00:05:39,319 --> 00:05:41,079 you don't know that each atom has eight sulfurs. 132 00:05:41,079 --> 00:05:43,430 You just have a big bag of sulfur. 133 00:05:43,430 --> 00:05:45,050 So, the imperative formula, there's only one 134 00:05:45,050 --> 00:05:46,060 atom in this molecule. 135 00:05:46,060 --> 00:05:49,519 You divide by eight and you get S. 136 00:05:49,519 --> 00:05:51,669 So you just know that all you've got there is sulfur. 137 00:05:51,670 --> 00:05:54,050 So let's just do one more. 138 00:05:54,050 --> 00:05:55,300 Glucose. 139 00:05:55,300 --> 00:05:57,555 140 00:05:57,555 --> 00:05:59,490 I'll pick a new color. 141 00:05:59,490 --> 00:06:00,250 Glucose. 142 00:06:00,250 --> 00:06:11,759 The molecular formula is C6H12O6. 143 00:06:11,759 --> 00:06:14,930 So for every carbon, there are how many? 144 00:06:14,930 --> 00:06:18,240 For every 6 carbons, there's 12 hydrogen and 1 oxygen. 145 00:06:18,240 --> 00:06:22,319 So if you kind of reduce this formula to its empirical form, 146 00:06:22,319 --> 00:06:23,269 what do you get? 147 00:06:23,269 --> 00:06:28,930 Let's see, you can divide all these numbers by 6, so we get 148 00:06:28,930 --> 00:06:33,180 1 carbon, 2 hydrogens, and 1 oxygen. 149 00:06:33,180 --> 00:06:35,720 So this just tells you the ratio that they exist in a big 150 00:06:35,720 --> 00:06:37,540 bag of this molecule. 151 00:06:37,540 --> 00:06:39,400 This tells you the exact number of 152 00:06:39,399 --> 00:06:41,389 atoms in that molecule. 153 00:06:41,389 --> 00:06:42,019 Fair enough. 154 00:06:42,019 --> 00:06:44,279 So now we know a little bit of the difference between 155 00:06:44,279 --> 00:06:48,119 molecular formula, and empirical formula, and 156 00:06:48,120 --> 00:06:48,759 structural formula. 157 00:06:48,759 --> 00:06:51,399 Now let's see if we can use what we know about the 158 00:06:51,399 --> 00:06:53,779 formulas and the periodic table to think a little bit 159 00:06:53,779 --> 00:06:59,329 about the composition, the mass composition, of some of 160 00:06:59,329 --> 00:07:01,439 these molecules. 161 00:07:01,439 --> 00:07:03,459 So the first thing to even think about is, how do you 162 00:07:03,459 --> 00:07:05,500 figure out the molecular mass? 163 00:07:05,500 --> 00:07:06,560 Right? 164 00:07:06,560 --> 00:07:08,050 I have my little periodic table down there. 165 00:07:08,050 --> 00:07:09,300 So molecular mass. 166 00:07:09,300 --> 00:07:18,579 167 00:07:18,579 --> 00:07:21,539 So the first question is, how do you figure out-- I mean, 168 00:07:21,540 --> 00:07:24,850 the molecular mass is going to be the sum of all of the atoms 169 00:07:24,850 --> 00:07:26,610 in that molecule, right? 170 00:07:26,610 --> 00:07:30,960 So if you wanted to know the molecular mass of-- let's say 171 00:07:30,959 --> 00:07:33,339 you wanted to know how much does one 172 00:07:33,339 --> 00:07:36,379 molecule of benzene mass? 173 00:07:36,379 --> 00:07:38,699 I don't want to say weight, because it should be 174 00:07:38,699 --> 00:07:40,969 independent of what planet you're on. 175 00:07:40,970 --> 00:07:45,160 So what is the mass of one molecule of benzene? 176 00:07:45,160 --> 00:07:49,890 Well, all you do is you add up the masses of the different 177 00:07:49,889 --> 00:07:50,569 constituents. 178 00:07:50,569 --> 00:07:53,110 So you have 6 carbons and 6 hydrogens. 179 00:07:53,110 --> 00:07:54,360 So let's do benzene. 180 00:07:54,360 --> 00:07:58,410 181 00:07:58,410 --> 00:08:01,570 You have 6 carbons and 6 hydrogens. 182 00:08:01,569 --> 00:08:03,680 So what's the mass of each carbon? 183 00:08:03,680 --> 00:08:06,470 So let's go back down to the periodic table. 184 00:08:06,470 --> 00:08:09,290 Just to give proper credit, I got this off of the Los Alamos 185 00:08:09,290 --> 00:08:12,689 National Laboratories website. 186 00:08:12,689 --> 00:08:14,680 So let's see, the atomic mass of carbon. 187 00:08:14,680 --> 00:08:16,519 The reason why I used this one instead of my previous one is 188 00:08:16,519 --> 00:08:20,039 my previous periodic table that I got off Wikipedia only 189 00:08:20,040 --> 00:08:21,490 had atomic numbers on them. 190 00:08:21,490 --> 00:08:24,199 But now that we're actually going to start talking about 191 00:08:24,199 --> 00:08:26,259 the mass composition of different atoms 192 00:08:26,259 --> 00:08:26,995 or different molecules. 193 00:08:26,995 --> 00:08:28,209 We're going to have to start looking at the 194 00:08:28,209 --> 00:08:29,859 atomic mass, right? 195 00:08:29,860 --> 00:08:32,269 Remember, the atomic mass, when you think about atomic 196 00:08:32,269 --> 00:08:36,808 mass units, it's just the number of protons plus the 197 00:08:36,808 --> 00:08:37,279 number of neutrons. 198 00:08:37,279 --> 00:08:39,399 So you have six protons in carbon 199 00:08:39,399 --> 00:08:40,850 and roughly six neutrons. 200 00:08:40,850 --> 00:08:41,889 And why is there this decimal? 201 00:08:41,889 --> 00:08:45,059 Because, as we said before, this is an average of all of 202 00:08:45,059 --> 00:08:49,359 the masses of the isotopes you'll find of carbon. 203 00:08:49,360 --> 00:08:51,669 So there's a little bit of carbon 14 on the planet, very 204 00:08:51,669 --> 00:08:54,099 little, but most of the carbon is carbon 12. 205 00:08:54,100 --> 00:08:57,200 When you proportionately average them, you get 12.01. 206 00:08:57,200 --> 00:09:00,280 But let's say we're dealing with carbon 12, just because 207 00:09:00,279 --> 00:09:01,529 that's the most common element. 208 00:09:01,529 --> 00:09:09,899 209 00:09:09,899 --> 00:09:13,409 Carbon is 12 atomic mass units. 210 00:09:13,409 --> 00:09:13,870 Right? 211 00:09:13,870 --> 00:09:16,039 And atomic mass units is a unit of mass. 212 00:09:16,039 --> 00:09:18,099 And we'll talk about how small it is. 213 00:09:18,100 --> 00:09:21,040 It's a very, very, very, very small fraction 214 00:09:21,039 --> 00:09:22,329 of a gram or kilogram. 215 00:09:22,330 --> 00:09:25,120 And we'll talk about that, probably in the next video. 216 00:09:25,120 --> 00:09:27,490 So carbon is 12 atomic mass units. 217 00:09:27,490 --> 00:09:29,590 What about hydrogen? 218 00:09:29,590 --> 00:09:30,190 Let's see. 219 00:09:30,190 --> 00:09:32,250 We go to our periodic table. 220 00:09:32,250 --> 00:09:33,980 Hydrogen is here in this dark blue. 221 00:09:33,980 --> 00:09:36,600 And I don't know if you can read it, but this is 222 00:09:36,600 --> 00:09:39,550 interesting, the atomic number of hydrogen is 1. 223 00:09:39,549 --> 00:09:45,269 The atomic mass of hydrogen is 1.0008. 224 00:09:45,269 --> 00:09:48,189 So that tells us that most of the hydrogen on this planet 225 00:09:48,190 --> 00:09:50,850 has an atomic mass of 1. 226 00:09:50,850 --> 00:09:53,850 Which tells us that it essentially has no neutrons. 227 00:09:53,850 --> 00:09:56,970 That hydrogen is a kind of an interesting nucleus there, 228 00:09:56,970 --> 00:09:58,519 where there is really just a proton. 229 00:09:58,519 --> 00:10:00,579 Just a proton sitting in that nucleus. 230 00:10:00,580 --> 00:10:03,670 And so if you were to ionize hydrogen. 231 00:10:03,669 --> 00:10:05,929 If you were to turn into a cation and take one of its 232 00:10:05,929 --> 00:10:08,239 electrons away, what are you left with? 233 00:10:08,240 --> 00:10:09,879 You just have a proton. 234 00:10:09,879 --> 00:10:13,789 A proton sitting by itself, just a single proton, really 235 00:10:13,789 --> 00:10:17,539 is no different than a hydrogen ion. 236 00:10:17,539 --> 00:10:19,219 And that to me is kind of interesting. 237 00:10:19,220 --> 00:10:20,600 That hydrogen is that simple. 238 00:10:20,600 --> 00:10:23,050 It's really just a proton. 239 00:10:23,049 --> 00:10:25,490 So hydrogen has an atomic mass of 1. 240 00:10:25,490 --> 00:10:27,580 Right? 241 00:10:27,580 --> 00:10:31,210 If it had any neutrons in it, it would have been at least an 242 00:10:31,210 --> 00:10:32,230 atomic mass of 2. 243 00:10:32,230 --> 00:10:35,350 But hydrogen has atomic mass of 1. 244 00:10:35,350 --> 00:10:37,769 One atomic mass unit. 245 00:10:37,769 --> 00:10:43,329 So what is the mass of one molecule of benzene? 246 00:10:43,330 --> 00:10:45,620 Well it's 6 times the carbon mass. 247 00:10:45,620 --> 00:10:51,610 6 times 12 plus 6 times the mass of hydrogen. 248 00:10:51,610 --> 00:10:52,769 Plus 6 times 1. 249 00:10:52,769 --> 00:10:59,634 So that is 6 times 12, is 72, plus 6 times 1, plus 6, is 250 00:10:59,634 --> 00:11:01,980 equal to 78. 251 00:11:01,980 --> 00:11:04,950 Now, what if someone said, what percent 252 00:11:04,950 --> 00:11:08,470 of benzene is carbon? 253 00:11:08,470 --> 00:11:10,450 Well then you say, OK, this is the piece that's 254 00:11:10,450 --> 00:11:12,370 carbon, right here. 255 00:11:12,370 --> 00:11:17,730 The carbon piece of benzene is 72 atomic mass units. 256 00:11:17,730 --> 00:11:18,889 Right, that's carbon. 257 00:11:18,889 --> 00:11:21,669 So what percentage of benzene is carbon? 258 00:11:21,669 --> 00:11:23,769 Well it's 72 over 78. 259 00:11:23,769 --> 00:11:24,949 The whole thing is 78. 260 00:11:24,950 --> 00:11:28,450 So it's 72 over 78. 261 00:11:28,450 --> 00:11:29,730 And what does that equal? 262 00:11:29,730 --> 00:11:32,110 Let me get a calculator going. 263 00:11:32,110 --> 00:11:36,560 264 00:11:36,559 --> 00:11:38,649 I should've had my calculator open ahead of time. 265 00:11:38,649 --> 00:11:42,579 266 00:11:42,580 --> 00:11:43,680 All right. 267 00:11:43,679 --> 00:11:51,819 So 72 divided by 78 is equal to 92.3%. 268 00:11:51,820 --> 00:12:00,510 So benzene is 92.3% carbon by mass. 269 00:12:00,509 --> 00:12:03,950 And of course, the remainder, the 7.7%, 270 00:12:03,950 --> 00:12:05,790 is going to be hydrogen. 271 00:12:05,789 --> 00:12:08,879 Let's do that for a couple of these other guys down here. 272 00:12:08,879 --> 00:12:11,820 So let's say we wanted to know what is the mass of 273 00:12:11,820 --> 00:12:13,490 a molecule of water? 274 00:12:13,490 --> 00:12:14,120 Fair enough. 275 00:12:14,120 --> 00:12:16,279 There's enough water on the planet, if you want to know 276 00:12:16,279 --> 00:12:16,779 what that is. 277 00:12:16,779 --> 00:12:19,980 Well we already know what the mass of a hydrogen is. 278 00:12:19,980 --> 00:12:20,950 It's 1. 279 00:12:20,950 --> 00:12:21,180 Right? 280 00:12:21,179 --> 00:12:23,250 Hydrogen is 1. 281 00:12:23,250 --> 00:12:25,840 One atomic mass unit. 282 00:12:25,840 --> 00:12:27,879 Oxygen is what? 283 00:12:27,879 --> 00:12:30,639 Oxygen is 16. 284 00:12:30,639 --> 00:12:32,929 Notice, it's exactly 16. 285 00:12:32,929 --> 00:12:37,169 So on most of the planet, you pretty much have, in an oxygen 286 00:12:37,169 --> 00:12:41,889 atom, you have 8 protons and exactly 8 neutrons. 287 00:12:41,889 --> 00:12:45,049 So you get an atomic mass of 16. 288 00:12:45,049 --> 00:12:49,539 So oxygen has an atomic mass of 16 atomic mass units. 289 00:12:49,539 --> 00:12:52,579 So the atomic mass of the entire molecule, you have 2 290 00:12:52,580 --> 00:12:57,970 hydrogens, so you have 2 times the mass of hydrogen plus 1 291 00:12:57,970 --> 00:13:03,100 oxygen-- plus 16-- so that equals 18 atomic 292 00:13:03,100 --> 00:13:06,519 mass units for water. 293 00:13:06,519 --> 00:13:09,970 And once again, if you want to say, what percent by mass of 294 00:13:09,970 --> 00:13:12,509 water is oxygen? 295 00:13:12,509 --> 00:13:14,529 Well it's 16 out of the 18, right? 296 00:13:14,529 --> 00:13:15,329 Is oxygen. 297 00:13:15,330 --> 00:13:19,360 So if we get the calculator back, you get 16 298 00:13:19,360 --> 00:13:22,710 divided by 18 is water. 299 00:13:22,710 --> 00:13:26,629 So, let's say you round it, 88.9% water. 300 00:13:26,629 --> 00:13:34,279 Sorry, 88.9% oxygen. 301 00:13:34,279 --> 00:13:36,699 So most of water is oxygen. 302 00:13:36,700 --> 00:13:39,720 And this is interesting, even though you have two hydrogens 303 00:13:39,720 --> 00:13:45,550 here, two hydrogens for every one oxygen, oxygen's mass is 304 00:13:45,549 --> 00:13:48,490 so much larger-- it's 16 times larger-- that 305 00:13:48,490 --> 00:13:51,664 most of water is oxygen. 306 00:13:51,664 --> 00:13:54,509 307 00:13:54,509 --> 00:13:56,539 Well, I'm probably running out of time, so the next video I'm 308 00:13:56,539 --> 00:13:57,959 going to talk about how do we go backwards. 309 00:13:57,960 --> 00:14:00,379 If someone gives you the composition, how can you get 310 00:14:00,379 --> 00:14:01,710 the empirical formula. 311 00:14:01,710 --> 00:14:03,950 Actually on a side note, slightly unrelated to what I 312 00:14:03,950 --> 00:14:09,140 just talked about, I was doing some research last night about 313 00:14:09,139 --> 00:14:11,019 metals, because they're actually interesting, about 314 00:14:11,019 --> 00:14:13,804 why some metals conduct more and some conduct less. 315 00:14:13,804 --> 00:14:16,319 316 00:14:16,320 --> 00:14:18,480 Because when I first talked about, you know, these were 317 00:14:18,480 --> 00:14:19,870 obviously the transition metals. 318 00:14:19,870 --> 00:14:22,159 They're backfilling their d orbitals. 319 00:14:22,159 --> 00:14:28,579 And I said, hey, the periodic table that was in-- I think I 320 00:14:28,580 --> 00:14:30,930 was looking in a Princeton Review book that described 321 00:14:30,929 --> 00:14:33,949 these as metals and described these as transition metals. 322 00:14:33,950 --> 00:14:36,350 And I was like, hey, you know, that's kind of not fair, 323 00:14:36,350 --> 00:14:41,470 because I consider iron and copper and gold and silver to 324 00:14:41,470 --> 00:14:43,149 be as metallic as anything. 325 00:14:43,149 --> 00:14:46,120 Why should these be called transition metals and these be 326 00:14:46,120 --> 00:14:47,379 just called regular metals. 327 00:14:47,379 --> 00:14:50,309 And it actually turns out that a common name for these are 328 00:14:50,309 --> 00:14:52,339 poor metals. 329 00:14:52,340 --> 00:14:54,570 Poor metals. 330 00:14:54,570 --> 00:14:57,580 Because, to a large degree, they're softer, they have 331 00:14:57,580 --> 00:15:00,780 lower melting points, so the intuition was right. 332 00:15:00,779 --> 00:15:05,579 To a large degree, when we think of metals, these are the 333 00:15:05,580 --> 00:15:06,610 metals I think of. 334 00:15:06,610 --> 00:15:10,560 And when we think of metallic nature in a chemistry sense-- 335 00:15:10,559 --> 00:15:13,139 we talked a lot about that, who wants to donate their 336 00:15:13,139 --> 00:15:15,490 electrons the most, that's metallic nature. 337 00:15:15,490 --> 00:15:17,000 They're the guys down here. 338 00:15:17,000 --> 00:15:19,179 And as you go to the top right, these want to donate 339 00:15:19,179 --> 00:15:21,539 their electrons the least. These are the most 340 00:15:21,539 --> 00:15:22,189 electronegative. 341 00:15:22,190 --> 00:15:24,690 They like electrons the most, so they actually have some of 342 00:15:24,690 --> 00:15:27,210 the worst metallic nature, so it actually makes sense to 343 00:15:27,210 --> 00:15:30,320 call them poor metals. 344 00:15:30,320 --> 00:15:32,170 And there's some debate on whether these should even be 345 00:15:32,169 --> 00:15:33,799 called poor metals. 346 00:15:33,799 --> 00:15:36,079 If you look up a bunch of periodic tables, some will 347 00:15:36,080 --> 00:15:37,460 call these metals. 348 00:15:37,460 --> 00:15:38,830 Some will call these poor metals. 349 00:15:38,830 --> 00:15:40,830 But I just wanted to throw that out there just so you're 350 00:15:40,830 --> 00:15:41,800 exposed to it. 351 00:15:41,799 --> 00:15:44,199 And so, you know, for me, it is a little bit more intuitive 352 00:15:44,200 --> 00:15:46,790 to call these poor metals, because they have less 353 00:15:46,789 --> 00:15:49,329 metallic nature than the stuff, especially down here, 354 00:15:49,330 --> 00:15:51,970 the alkali and the alkaline earth metals. 355 00:15:51,970 --> 00:15:54,060 Anyway, see you in the next video.