1 00:00:00,000 --> 00:00:00,940 2 00:00:00,940 --> 00:00:04,349 So far, we've learned a little bit about determining electron 3 00:00:04,349 --> 00:00:05,209 configurations. 4 00:00:05,209 --> 00:00:08,589 Let's see if we can use that information to group elements 5 00:00:08,589 --> 00:00:12,439 on the periodic table and then guess as to what they might do 6 00:00:12,439 --> 00:00:14,129 when they react with other elements. 7 00:00:14,130 --> 00:00:16,890 So let's just figure out the electron configurations of a 8 00:00:16,890 --> 00:00:18,679 couple of elements just for a little bit of practice. 9 00:00:18,679 --> 00:00:20,920 So, lithium, right there. 10 00:00:20,920 --> 00:00:22,630 What does it look like? 11 00:00:22,629 --> 00:00:25,969 Lithium's electron configuration. 12 00:00:25,969 --> 00:00:29,669 You get the first shell, is 1s2. 13 00:00:29,670 --> 00:00:31,200 Two electrons there. 14 00:00:31,199 --> 00:00:34,839 And then you have 2s1. 15 00:00:34,840 --> 00:00:37,270 And sometimes, just to be quick, to get the notation, is 16 00:00:37,270 --> 00:00:40,280 you can imagine lithium's electron configuration is the 17 00:00:40,280 --> 00:00:43,969 exact same thing as helium's electron configuration-- this 18 00:00:43,969 --> 00:00:47,070 is helium's electron configuration-- plus the 2s1. 19 00:00:47,070 --> 00:00:49,939 This could have also been written as-- do that in light 20 00:00:49,939 --> 00:00:56,689 blue-- could also have been written as helium, 2s1. 21 00:00:56,689 --> 00:00:58,809 Which essentially means that lithium's electron 22 00:00:58,810 --> 00:01:01,330 configuration is exactly what you would have written for 23 00:01:01,329 --> 00:01:03,359 helium's electron configuration, and then you'd 24 00:01:03,359 --> 00:01:04,390 have written 2s1. 25 00:01:04,390 --> 00:01:05,959 You could do that a bunch of times. 26 00:01:05,959 --> 00:01:07,719 Let's say if we wanted to figure out the electron 27 00:01:07,719 --> 00:01:11,980 configuration of iron. 28 00:01:11,980 --> 00:01:14,180 Instead of going through the whole thing, you know, it's 29 00:01:14,180 --> 00:01:18,950 1s2, and then it's 2s2, and 2p6. 30 00:01:18,950 --> 00:01:20,359 Instead of doing that whole thing, you could just say, OK, 31 00:01:20,359 --> 00:01:23,129 iron has the same electron configuration. 32 00:01:23,129 --> 00:01:26,179 So you could say iron's electron configuration is the 33 00:01:26,180 --> 00:01:32,375 same thing as argon's electron configuration. 34 00:01:32,375 --> 00:01:36,140 So I'll just put argon in brackets. 35 00:01:36,140 --> 00:01:38,750 And then you get 4s2. 36 00:01:38,750 --> 00:01:43,200 37 00:01:43,200 --> 00:01:48,280 And then you have one, two, three, four, five, six. 38 00:01:48,280 --> 00:01:49,750 So d6. 39 00:01:49,750 --> 00:01:53,629 And we learned that when you're in the d subshell, or 40 00:01:53,629 --> 00:01:56,739 when you're in the d-block of the periodic table, you are 41 00:01:56,739 --> 00:02:01,349 actually backfilling the previous shell. 42 00:02:01,349 --> 00:02:04,829 So when we're in the fourth period, in the d-block, we're 43 00:02:04,829 --> 00:02:06,849 backfilling the third shell. 44 00:02:06,849 --> 00:02:09,930 So 3d6. 45 00:02:09,930 --> 00:02:11,870 And someone had asked-- and this is an interesting 46 00:02:11,870 --> 00:02:13,740 question-- why does it do that? 47 00:02:13,740 --> 00:02:15,230 Why does it not just continue? 48 00:02:15,229 --> 00:02:17,889 Why doesn't it fill the fourth d shell? 49 00:02:17,889 --> 00:02:20,789 And the way I think about it-- and this is all intuition, and 50 00:02:20,789 --> 00:02:23,509 things at the atomic level really start to become, on 51 00:02:23,509 --> 00:02:25,879 some levels, non-intuitive-- but the way I think about is 52 00:02:25,879 --> 00:02:30,090 as the atom grows larger and larger, there are more spaces 53 00:02:30,090 --> 00:02:31,509 between the previous orbitals. 54 00:02:31,509 --> 00:02:36,560 For example, this is just how I visualize it. 55 00:02:36,560 --> 00:02:39,430 If my first shell looks like this. 56 00:02:39,430 --> 00:02:41,260 Let's say the s looks like this. 57 00:02:41,259 --> 00:02:44,439 And then, if I just cut it out, let's say the p's look 58 00:02:44,439 --> 00:02:45,689 like something like this. 59 00:02:45,689 --> 00:02:49,000 60 00:02:49,000 --> 00:02:51,810 This is maybe the second shell. 61 00:02:51,810 --> 00:02:53,060 The p's look like this. 62 00:02:53,060 --> 00:02:55,210 And then the next place an electron might want to be 63 00:02:55,210 --> 00:02:59,150 might be in the third shell, right? 64 00:02:59,150 --> 00:03:03,900 So the third shell would be like this. 65 00:03:03,900 --> 00:03:07,969 And then you fill out the third p shell. 66 00:03:07,969 --> 00:03:09,289 This is just an intuition. 67 00:03:09,289 --> 00:03:10,829 This isn't exactly what an electron would look like. 68 00:03:10,830 --> 00:03:13,540 Maybe the third p shell would look something like that. 69 00:03:13,539 --> 00:03:16,859 70 00:03:16,860 --> 00:03:19,470 Look something like that. 71 00:03:19,469 --> 00:03:21,909 And then look something like that. 72 00:03:21,909 --> 00:03:24,020 And then you're in the fourth shell. 73 00:03:24,020 --> 00:03:27,520 So you're doing the fourth shell. 74 00:03:27,520 --> 00:03:31,650 The s subshell might look something like that. 75 00:03:31,650 --> 00:03:35,230 And then instead of immediately starting the next 76 00:03:35,229 --> 00:03:39,310 p shell, you're in the d-block now. 77 00:03:39,310 --> 00:03:44,830 So this is-- let me just write some labels-- 4s. 78 00:03:44,830 --> 00:03:46,920 This is 3s. 79 00:03:46,919 --> 00:03:50,019 This is 3p. 80 00:03:50,020 --> 00:03:52,500 This is 2p. 81 00:03:52,500 --> 00:03:53,930 This is 2s. 82 00:03:53,930 --> 00:03:56,770 83 00:03:56,770 --> 00:03:58,650 And then 1s is inside of 2s. 84 00:03:58,650 --> 00:03:59,980 So you don't have to worry about that too much. 85 00:03:59,979 --> 00:04:04,389 But my intuition behind why the d orbital gets backfilled 86 00:04:04,389 --> 00:04:07,349 is because now, as the atom gets larger and larger, you 87 00:04:07,349 --> 00:04:09,829 have these spaces in between the previous orbital. 88 00:04:09,830 --> 00:04:18,790 So now, after filling the 4s subshell, or the 4s orbital-- 89 00:04:18,790 --> 00:04:23,689 so this is 4s here-- out here, we go back and we fill in the 90 00:04:23,689 --> 00:04:24,959 3d orbital. 91 00:04:24,959 --> 00:04:26,979 So we're going back and we're filling these 92 00:04:26,980 --> 00:04:30,450 spaces right here. 93 00:04:30,449 --> 00:04:32,579 So this is a lower energy state than this. 94 00:04:32,579 --> 00:04:36,729 It takes more energy to cram an electron back into the 3d 95 00:04:36,730 --> 00:04:38,530 shell, back there. 96 00:04:38,529 --> 00:04:42,179 But then once you do that, now you're ready to then go to the 97 00:04:42,180 --> 00:04:48,120 4p shell, which might look something like this. 98 00:04:48,120 --> 00:04:51,610 So an electron would rather go to another shell, which is the 99 00:04:51,610 --> 00:04:56,870 fourth shell, rather than backfill the 3d shells. 100 00:04:56,870 --> 00:04:58,949 But once it fills out the fourth shell, it fills in 101 00:04:58,949 --> 00:04:59,914 those spaces in between. 102 00:04:59,915 --> 00:05:02,689 And as the electron gets bigger and bigger, there's 103 00:05:02,689 --> 00:05:04,259 more and more spaces in between. 104 00:05:04,259 --> 00:05:06,939 So eventually, when the electron gets big enough, 105 00:05:06,939 --> 00:05:08,860 there's going to be spaces between the d shells, and 106 00:05:08,860 --> 00:05:12,930 that's where the d orbitals and that's where the f 107 00:05:12,930 --> 00:05:13,990 orbitals will go. 108 00:05:13,990 --> 00:05:15,610 That's my intuition behind its working. 109 00:05:15,610 --> 00:05:18,740 And obviously, when we're dealing at the atomic scale, 110 00:05:18,740 --> 00:05:21,050 as far as I'm concerned, that's the best that I can do. 111 00:05:21,050 --> 00:05:21,670 But fair enough. 112 00:05:21,670 --> 00:05:23,220 That's not what I want to do here, but that was a good 113 00:05:23,220 --> 00:05:27,580 question, as to why do you go and backfill the third shell 114 00:05:27,579 --> 00:05:29,289 when we're in the fourth period? 115 00:05:29,290 --> 00:05:29,750 Fair enough. 116 00:05:29,750 --> 00:05:34,500 This is an easy way to write iron's electron configuration. 117 00:05:34,500 --> 00:05:37,709 The reason why I'm doing all of this is to figure out how 118 00:05:37,709 --> 00:05:39,889 many electrons you have in the outermost shell. 119 00:05:39,889 --> 00:05:44,629 In the case of lithium, you have one electron in your 120 00:05:44,629 --> 00:05:45,680 outermost shell, right? 121 00:05:45,680 --> 00:05:47,860 This is your outermost shell right here. 122 00:05:47,860 --> 00:05:49,490 You have one electron. 123 00:05:49,490 --> 00:05:51,740 And you could have done the same thing right there. 124 00:05:51,740 --> 00:05:53,579 In the case of iron, how many electrons in 125 00:05:53,579 --> 00:05:55,000 the outermost shell? 126 00:05:55,000 --> 00:05:57,949 Remember, the outermost shell is the period you're in. 127 00:05:57,949 --> 00:06:00,569 And this is the outermost shell. 128 00:06:00,569 --> 00:06:03,259 So even though these are higher energy electrons-- it 129 00:06:03,259 --> 00:06:07,550 took more energy to backfill those into the lower energy 130 00:06:07,550 --> 00:06:11,629 shell-- it's these that are on the outside energy shell, the 131 00:06:11,629 --> 00:06:13,670 fourth shell, that are going to be the 132 00:06:13,670 --> 00:06:14,449 ones that are reacting. 133 00:06:14,449 --> 00:06:15,219 And how many are there? 134 00:06:15,220 --> 00:06:17,590 There are two. 135 00:06:17,589 --> 00:06:18,919 And this is an important thing. 136 00:06:18,920 --> 00:06:21,410 So there's two here. 137 00:06:21,410 --> 00:06:22,710 There's two on the outside shell here. 138 00:06:22,709 --> 00:06:24,939 And actually, there's going to be two for any of these in 139 00:06:24,939 --> 00:06:25,610 pink right here. 140 00:06:25,610 --> 00:06:28,879 Any of the ones in the d-block, what happens? 141 00:06:28,879 --> 00:06:30,730 You fill whatever period you're in. 142 00:06:30,730 --> 00:06:33,310 Let's say that you're in period five here. 143 00:06:33,310 --> 00:06:33,670 Right? 144 00:06:33,670 --> 00:06:35,850 You're going to have 5s1. 145 00:06:35,850 --> 00:06:37,240 5s2. 146 00:06:37,240 --> 00:06:39,050 And then you're going to go back and you're going to fill 147 00:06:39,050 --> 00:06:40,490 the 4d shell. 148 00:06:40,490 --> 00:06:41,189 Right? 149 00:06:41,189 --> 00:06:43,240 But in terms of how many electrons you have on the 150 00:06:43,240 --> 00:06:46,199 outside shell, in this case the fifth shell, you are going 151 00:06:46,199 --> 00:06:47,659 to have two electrons. 152 00:06:47,660 --> 00:06:51,060 So all of these are going to have to electrons in their 153 00:06:51,060 --> 00:06:52,310 outermost shell. 154 00:06:52,310 --> 00:06:54,649 155 00:06:54,649 --> 00:06:56,831 In the case of these, the outermost electrons are going 156 00:06:56,831 --> 00:06:58,750 to be 4s2, right? 157 00:06:58,750 --> 00:07:01,209 Because then you go back and fill the 3d, but the outer 158 00:07:01,209 --> 00:07:03,000 ones are 4s2. 159 00:07:03,000 --> 00:07:04,639 So this one also has two electrons in 160 00:07:04,639 --> 00:07:05,930 its outermost shell. 161 00:07:05,930 --> 00:07:08,540 How many does this group have? 162 00:07:08,540 --> 00:07:10,939 And I've just used a word that I don't know if I've defined 163 00:07:10,939 --> 00:07:15,029 before, but the group are the columns in the periodic table. 164 00:07:15,029 --> 00:07:18,589 And as you can see, they all have patterns to them. 165 00:07:18,589 --> 00:07:21,989 Everything in this first group has one electron in its 166 00:07:21,990 --> 00:07:23,769 outermost shell. 167 00:07:23,769 --> 00:07:26,089 If you don't believe me, look at hydrogen. 168 00:07:26,089 --> 00:07:28,509 Hydrogen's electron configuration is 1s1. 169 00:07:28,509 --> 00:07:30,925 Its outermost shell is 1s. 170 00:07:30,925 --> 00:07:33,620 It has one electron there. 171 00:07:33,620 --> 00:07:33,959 Right? 172 00:07:33,959 --> 00:07:35,189 And that's true for all of these. 173 00:07:35,189 --> 00:07:36,985 All of these guys have two electrons in 174 00:07:36,985 --> 00:07:38,480 their outermost shell. 175 00:07:38,480 --> 00:07:40,930 These guys have those same two electrons. 176 00:07:40,930 --> 00:07:42,780 We can view it that way, in their outermost shell, but 177 00:07:42,779 --> 00:07:44,529 then they go and backfill the d shell. 178 00:07:44,529 --> 00:07:45,609 But in terms of their outermost 179 00:07:45,610 --> 00:07:48,460 shell, only two electrons. 180 00:07:48,459 --> 00:07:52,620 Than once you fill the d-block, or you go backfill, 181 00:07:52,620 --> 00:07:55,670 in the case of the fourth period, you go and backfill 182 00:07:55,670 --> 00:07:58,569 the third d sub-orbital. 183 00:07:58,569 --> 00:08:01,659 Then you go back to filling the fourth shell again. 184 00:08:01,660 --> 00:08:03,860 Now the p block, right? 185 00:08:03,860 --> 00:08:09,540 So this one's going to have three electrons 186 00:08:09,540 --> 00:08:11,010 in its outside orbital. 187 00:08:11,009 --> 00:08:14,060 Or you could say three valence electrons. 188 00:08:14,060 --> 00:08:19,709 This is four, five, six, seven, and eight. 189 00:08:19,709 --> 00:08:22,620 Let me do one more, just in case you don't believe me. 190 00:08:22,620 --> 00:08:28,269 What's the electron configuration for Sn. 191 00:08:28,269 --> 00:08:30,919 This is, what, selenium? 192 00:08:30,920 --> 00:08:31,740 I'm not even sure. 193 00:08:31,740 --> 00:08:32,690 But let's say Sn. 194 00:08:32,690 --> 00:08:34,210 What's the electron configuration? 195 00:08:34,210 --> 00:08:35,620 It's going to have the same electron 196 00:08:35,620 --> 00:08:38,639 configuration as krypton. 197 00:08:38,639 --> 00:08:40,408 Yes, that element is krypton. 198 00:08:40,408 --> 00:08:42,788 There is such an element. 199 00:08:42,788 --> 00:08:44,069 So it will have the same electron 200 00:08:44,070 --> 00:08:45,520 configuration as krypton. 201 00:08:45,519 --> 00:08:47,120 So I could have figured out krypton's electron 202 00:08:47,120 --> 00:08:48,919 configuration just by going through the whole periodic 203 00:08:48,919 --> 00:08:51,019 table, but this is just a faster way of doing it. 204 00:08:51,019 --> 00:08:53,419 Same thing as krypton, and then it has 5s2. 205 00:08:53,419 --> 00:08:58,459 206 00:08:58,460 --> 00:09:00,940 Then it goes back and backfills the d-block. 207 00:09:00,940 --> 00:09:02,470 So then there's 10 there. 208 00:09:02,470 --> 00:09:07,129 So 4d10. 209 00:09:07,129 --> 00:09:09,379 And then it starts filling up the p-block in 210 00:09:09,379 --> 00:09:10,389 the fifth shell again. 211 00:09:10,389 --> 00:09:11,639 So 5p2. 212 00:09:11,639 --> 00:09:14,629 213 00:09:14,629 --> 00:09:16,929 So how many valence electrons does it have? 214 00:09:16,929 --> 00:09:19,309 Valence electrons, or electrons in 215 00:09:19,309 --> 00:09:21,439 the outermost shell? 216 00:09:21,440 --> 00:09:22,800 Well, what's the outermost shell? 217 00:09:22,799 --> 00:09:24,250 It's the fifth shell. 218 00:09:24,250 --> 00:09:29,440 So these and these. 219 00:09:29,440 --> 00:09:31,750 These electrons have a higher energy state than that. 220 00:09:31,750 --> 00:09:33,960 It took a little bit more energy to cram them back into 221 00:09:33,960 --> 00:09:35,800 that previous shell than it took to put 222 00:09:35,799 --> 00:09:37,309 these on the s orbital. 223 00:09:37,309 --> 00:09:39,629 But if you talk about the electrons that will react, and 224 00:09:39,629 --> 00:09:41,830 that's why I'm emphasizing these, these are the electrons 225 00:09:41,830 --> 00:09:47,129 that are going to react with other atoms. Or sometimes with 226 00:09:47,129 --> 00:09:49,840 just other electrons, even. 227 00:09:49,840 --> 00:09:52,460 This one has four outside electrons. 228 00:09:52,460 --> 00:09:53,920 And you see that right there. 229 00:09:53,919 --> 00:09:55,699 Four outside electrons. 230 00:09:55,700 --> 00:09:58,900 And since the outside electrons, for the most part, 231 00:09:58,899 --> 00:10:03,129 are the ones that you're going to care about, there's a-- I 232 00:10:03,129 --> 00:10:05,750 guess you could say, a notation where you only draw 233 00:10:05,750 --> 00:10:07,129 the outermost electrons. 234 00:10:07,129 --> 00:10:10,820 So, let's say, for hydrogen, you could write it like this. 235 00:10:10,820 --> 00:10:14,150 Where you're only drawing the outermost, valence electrons. 236 00:10:14,149 --> 00:10:16,069 Valence electrons are just the outermost electrons. 237 00:10:16,070 --> 00:10:17,540 You could write it like that. 238 00:10:17,539 --> 00:10:19,039 You could write it like that. 239 00:10:19,039 --> 00:10:21,149 But this says, hey, I just have one outside 240 00:10:21,149 --> 00:10:22,980 electron for hydrogen. 241 00:10:22,980 --> 00:10:25,379 If I wanted to draw it for iron? 242 00:10:25,379 --> 00:10:26,899 Iron, right here? 243 00:10:26,899 --> 00:10:27,519 How would I do that? 244 00:10:27,519 --> 00:10:31,169 I have two electrons in my outermost shell, so iron I 245 00:10:31,169 --> 00:10:33,889 could just do like this. 246 00:10:33,889 --> 00:10:36,129 And electrons, they tend to be paired. 247 00:10:36,129 --> 00:10:40,049 So if I have, let's say I wanted to take the example of, 248 00:10:40,049 --> 00:10:42,809 if this is Sn, this is selenium. 249 00:10:42,809 --> 00:10:44,269 Let me do carbon. 250 00:10:44,269 --> 00:10:47,840 Carbon, I have four electrons in my outermost shell. 251 00:10:47,840 --> 00:10:49,470 So carbon I could write like this. 252 00:10:49,470 --> 00:10:54,399 253 00:10:54,399 --> 00:10:58,750 Or if I didn't want to pair them, in theory I could write 254 00:10:58,750 --> 00:11:01,220 them like that as well. 255 00:11:01,220 --> 00:11:04,009 And now they're ready to react with other things. 256 00:11:04,009 --> 00:11:06,799 Now what does this tell me about, you know, this one has 257 00:11:06,799 --> 00:11:09,409 one electron in its outermost shell. 258 00:11:09,409 --> 00:11:13,389 These blue, these noble gases-- and we'll talk a 259 00:11:13,389 --> 00:11:16,689 little bit about them in a second-- have eight electrons 260 00:11:16,690 --> 00:11:17,380 in the outermost shell. 261 00:11:17,379 --> 00:11:19,559 How does that help me when I'm actually trying to figure out 262 00:11:19,559 --> 00:11:21,199 how things react? 263 00:11:21,200 --> 00:11:25,730 Well, it turns out that all atoms want to have eight 264 00:11:25,730 --> 00:11:27,200 electrons in their outermost shell. 265 00:11:27,200 --> 00:11:28,660 And that number is important. 266 00:11:28,659 --> 00:11:30,000 Eight. 267 00:11:30,000 --> 00:11:34,320 They want to have eight electrons in 268 00:11:34,320 --> 00:11:35,870 their outermost shell. 269 00:11:35,870 --> 00:11:39,230 This is the most stable configuration for atoms. Or I 270 00:11:39,230 --> 00:11:43,050 guess you could say, to some degree, a better energy state 271 00:11:43,049 --> 00:11:43,979 for the atom. 272 00:11:43,980 --> 00:11:45,259 And why is it the number eight? 273 00:11:45,259 --> 00:11:48,019 Well, that's something to think about. 274 00:11:48,019 --> 00:11:49,980 This is another fundamental number that 275 00:11:49,980 --> 00:11:51,379 just pops out of nature. 276 00:11:51,379 --> 00:11:52,610 And I've thought a little bit about it. 277 00:11:52,610 --> 00:11:56,399 It must be something about the atoms in the outermost shell, 278 00:11:56,399 --> 00:11:58,759 when you have eight, they resonate well with each other. 279 00:11:58,759 --> 00:12:02,269 And they somehow don't get in the way of each other. 280 00:12:02,269 --> 00:12:03,779 Or don't want to push away from each other. 281 00:12:03,779 --> 00:12:04,949 I don't know the answer to that. 282 00:12:04,950 --> 00:12:07,280 And frankly, if someone could really answer the question of 283 00:12:07,279 --> 00:12:14,789 why eight, exactly why eight, they would make a good career 284 00:12:14,789 --> 00:12:17,139 for themselves in physics or chemistry. 285 00:12:17,139 --> 00:12:20,580 But through experimentation, it has been well established 286 00:12:20,580 --> 00:12:23,259 that atoms want to have eight electrons in 287 00:12:23,259 --> 00:12:24,990 their outermost shell. 288 00:12:24,990 --> 00:12:29,009 So the question is, if you're dealing with something like, 289 00:12:29,009 --> 00:12:32,029 let's say you're dealing with potassium. 290 00:12:32,029 --> 00:12:32,409 Right? 291 00:12:32,409 --> 00:12:38,139 Potassium has one electron in its outermost shell. 292 00:12:38,139 --> 00:12:46,240 Let's say you have stuff like chlorine, that has seven 293 00:12:46,240 --> 00:12:49,100 electrons in its outermost shell. 294 00:12:49,100 --> 00:12:50,970 What do you think's going to happen if you put some 295 00:12:50,970 --> 00:12:54,850 potassium near some chlorine? 296 00:12:54,850 --> 00:12:56,360 What's going to happen? 297 00:12:56,360 --> 00:13:02,560 Well, what's the easiest way for the chlorine 298 00:13:02,559 --> 00:13:03,524 to get eight electrons? 299 00:13:03,524 --> 00:13:05,980 Well it has seven in its outermost shell. 300 00:13:05,980 --> 00:13:06,610 What's the easiest way? 301 00:13:06,610 --> 00:13:10,039 Well, it'll want to gain an electron really, really badly. 302 00:13:10,039 --> 00:13:12,289 And what's the easiest way for potassium to have eight 303 00:13:12,289 --> 00:13:14,669 electrons in its outermost shell? 304 00:13:14,669 --> 00:13:17,860 Well, if it lost that one electron, then it will have 305 00:13:17,860 --> 00:13:20,340 eight electrons in its outermost shell, right? 306 00:13:20,340 --> 00:13:22,450 Its outermost shell won't be the fourth shell anymore. 307 00:13:22,450 --> 00:13:23,700 It'll be the third shell. 308 00:13:23,700 --> 00:13:25,950 But it'll have eight electrons in the third shell. 309 00:13:25,950 --> 00:13:29,820 Its configuration will then look like argon if it loses 310 00:13:29,820 --> 00:13:30,900 that one electron. 311 00:13:30,899 --> 00:13:33,720 So it'll be a more stable state. 312 00:13:33,720 --> 00:13:37,690 So if you put sodium in the presence of chlorine, what's 313 00:13:37,690 --> 00:13:38,650 going to happen? 314 00:13:38,649 --> 00:13:42,019 This electron wants to jump off of sodium real bad so that 315 00:13:42,019 --> 00:13:43,889 sodium can have eight electrons in its outermost 316 00:13:43,889 --> 00:13:47,679 shell, or have an electron configuration like argon. 317 00:13:47,679 --> 00:13:50,409 And that electron is going to jump to chlorine, and then 318 00:13:50,409 --> 00:13:52,709 chlorine will have eight electrons in its outermost 319 00:13:52,710 --> 00:13:54,070 shell, and also have an electron 320 00:13:54,070 --> 00:13:56,970 configuration like argon. 321 00:13:56,970 --> 00:14:01,560 And so, as you can imagine, this group right here, which 322 00:14:01,559 --> 00:14:05,029 are called the alkali metals. 323 00:14:05,029 --> 00:14:06,600 And we'll talk probably in the next video why 324 00:14:06,600 --> 00:14:08,230 they're called metals. 325 00:14:08,230 --> 00:14:09,810 This group here, alkali metals. 326 00:14:09,809 --> 00:14:11,629 And they tend to exclude hydrogen, and 327 00:14:11,629 --> 00:14:13,110 we'll talk about that. 328 00:14:13,110 --> 00:14:16,139 These really want to give away electrons. 329 00:14:16,139 --> 00:14:18,620 And because of that, they're highly, highly reactive, 330 00:14:18,620 --> 00:14:21,049 especially if you put them in the presence of these 331 00:14:21,049 --> 00:14:23,049 elements, these yellow elements right here, which are 332 00:14:23,049 --> 00:14:24,509 called the halogens. 333 00:14:24,509 --> 00:14:27,149 These really, really want to take electrons from other 334 00:14:27,149 --> 00:14:29,439 things, because they just need one to get to eight. 335 00:14:29,440 --> 00:14:31,750 They usually want to give away electrons, because they just 336 00:14:31,750 --> 00:14:34,639 have to give away one to get to eight. 337 00:14:34,639 --> 00:14:36,789 And the reason why hydrogen, actually, isn't included is 338 00:14:36,789 --> 00:14:39,059 because hydrogen doesn't want to give away its electron as 339 00:14:39,059 --> 00:14:41,929 bad as these guys. 340 00:14:41,929 --> 00:14:44,919 This rule that your outermost shell wants to get to eight, 341 00:14:44,919 --> 00:14:46,439 that's true for everything except for 342 00:14:46,440 --> 00:14:47,790 hydrogen and helium. 343 00:14:47,789 --> 00:14:50,309 Hydrogen and helium, just because they have one shell, 344 00:14:50,309 --> 00:14:52,329 they're happy with just two electrons. 345 00:14:52,330 --> 00:14:55,379 And so with hydrogen, sure, it could lose an electron, but 346 00:14:55,379 --> 00:14:57,860 could just as easily gain an electron and be happy, because 347 00:14:57,860 --> 00:15:00,539 it'll have a full first shell. 348 00:15:00,539 --> 00:15:04,509 But all of these other ones, these alkali metals, they want 349 00:15:04,509 --> 00:15:06,429 to give away electrons really bad. 350 00:15:06,429 --> 00:15:09,099 When people in chemistry talk about metallic nature, they're 351 00:15:09,100 --> 00:15:11,899 really talking about how badly something wants 352 00:15:11,899 --> 00:15:13,720 to give away electrons. 353 00:15:13,720 --> 00:15:15,259 Anyway, I'm all out of time now. 354 00:15:15,259 --> 00:15:17,960 In the next video, we'll continue discussing the groups 355 00:15:17,960 --> 00:15:20,620 in the periodic tables and any trends we can 356 00:15:20,620 --> 00:15:22,799 ascertain from them.