1
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2
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Let's figure out the electron configuration for nickel,

3
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right there.

4
00:00:07,299 --> 00:00:08,519
28 electrons.

5
00:00:08,519 --> 00:00:10,359
We just have to figure out what shells and

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orbitals they go in.

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00:00:11,539 --> 00:00:12,579
28 electrons.

8
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So the way we've learned to do it is, we

9
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defined this as the s-block.

10
00:00:16,000 --> 00:00:19,829
And we can just remember that helium actually belongs here

11
00:00:19,829 --> 00:00:22,349
when we talk about orbitals in the s-block.

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This is the d-block.

13
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This is the p-block.

14
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And so we could start with the lowest energy electrons.

15
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We could either work forward or work backwards.

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If we work forwards, first we fill up the first two

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00:00:34,630 --> 00:00:37,020
electrons going to 1s2.

18
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So remember we're doing nickel.

19
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So we fill up 1s2 first with two electrons.

20
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Then we go to 2s2.

21
00:00:48,784 --> 00:00:51,669
And remember this little small superscript 2 just means we're

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putting two electrons into that subshell

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or into that orbital.

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Actually, let me do each shell in a different color.

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So 2s2.

26
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Then we fill out 2p6.

27
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We fill out all of these, right there.

28
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So 2p6.

29
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Let's see, so far we've filled out 10 electrons.

30
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We've configured 10.

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You can do it that way.

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Now we're on the third shell.

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So now we go to 3s2.

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Remember, we're dealing with nickel, so we go to 3s2.

35
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36
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Then we fill out in the third shell the p orbital.

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So 3p6.

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We're in the third period, so that's 3p6, right there.

40
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There's six of them.

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And then we go to the fourth shell.

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I'll do it in yellow.

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So we do 4s2.

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45
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And now we're in the d-block.

46
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And so we're filling in one, two, three, four, five, six,

47
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seven, eight in this d-block.

48
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So it's going to say d8.

49
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And remember, it's not going to be 4d8.

50
00:02:03,010 --> 00:02:05,650
We're going to go and backfill the third shell.

51
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So it will be 3d8.

52
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So we could write 3d8 here.

53
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So this is the order in which we fill, from lowest energy

54
00:02:15,349 --> 00:02:18,419
state electrons to highest energy state.

55
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But notice the highest energy state electrons, which are

56
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these that we filled in, in the end, these eight, these

57
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went into the third shell.

58
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So when you're filling the d-block, you take the period

59
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that you're in minus one.

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So we were in the fourth period in the periodic table,

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but we subtracted one, right?

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This is 4 minus 1.

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So this is the electron configuration for nickel.

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And of course if we remember, if we care about the valence

65
00:02:45,789 --> 00:02:51,169
electrons, which electrons are in the outermost shell, then

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you would look at these right here.

67
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These are the electrons that will react, although these are

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in a higher energy state.

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And these react because they're the furthest. Or at

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least, the way I visualize them is that they have a

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higher probability of being further from the nucleus than

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these right here.

73
00:03:07,219 --> 00:03:11,060
Now, another way to figure out the electron configuration for

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nickel-- and this is covered in some chemistry classes,

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although I like the way we just did it because you look

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at the periodic table and you gain a familiarity with it,

77
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which is important, because then you'll start having an

78
00:03:21,509 --> 00:03:24,250
intuition for how different elements react with each

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other-- is to just say, OK, nickel has 28 electrons, if

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it's neutral.

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It has 28 electrons, because that's the same number of

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protons, which is the atomic number.

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Remember, 28 just tells you how many protons there are.

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This is the number of protons.

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We're assuming it's neutral.

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So it has the same number of electrons.

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That's not always going to be the case.

88
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But when you do these electron configurations, that tends to

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be the case.

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So if we say nickel has 28, has an atomic number of 28, so

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00:03:54,180 --> 00:03:56,430
it's electron configuration we can do it this way, too.

92
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We can write the energy shells.

93
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So one, two, three, four.

94
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And then on the top we write s, p, d.

95
00:04:08,979 --> 00:04:10,179
Well we're not going to get to f.

96
00:04:10,180 --> 00:04:13,510
But you could write f and g and h and keep going.

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What's going to happen is you're going to fill this one

98
00:04:15,080 --> 00:04:20,060
first, then you're going to fill this one, then that one,

99
00:04:20,060 --> 00:04:23,720
then this one, then this one.

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Let me actually draw it.

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00:04:24,560 --> 00:04:28,480
So what you do is, these are the shells that exist, period.

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These are the shells that exist, in green.

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00:04:30,949 --> 00:04:33,620
What I'm drawing now isn't the order that you fill them.

104
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This is just, they exist. So there is a 3d subshell.

105
00:04:38,930 --> 00:04:41,340
There's not a 3f subshell.

106
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There is a 4f subshell.

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Let me draw a line here, just so it becomes

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a little bit neater.

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And the way you fill them is you make these diagonals.

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So first you fill this s shell like that, then you fill this

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00:04:54,779 --> 00:04:55,619
one like that.

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Then you do this diagonal down like that.

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Then you do this diagonal down like that.

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And then this diagonal down like that.

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And you just have to know that there's only two can fit in s,

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six in p, in this case, 10 in d.

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And we can worry about f in the future, but if you look at

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the f-block on a periodic table, you know how many

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there are in f.

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So you fill it like that.

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So first you just say, OK.

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For nickel, 28 electrons.

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So first I fill this one out.

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So that's 1s2.

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126
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Then I go, there's no 1p, so then I go to 2s2.

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128
00:05:33,740 --> 00:05:34,840
Let me do this in a different color.

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So then I go right here, 2s2.

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That's that right there.

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Then I go up to this diagonal, and I come back down.

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And then there's 2p6.

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And you have to keep track of how many electrons you're

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dealing with, in this case.

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So we're up to 10 now.

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So we used that one up.

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Then the arrow tells us to go down here, so now we do the

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third energy shell.

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So 3s2.

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And then where do we go next?

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3s2.

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Then we follow the arrow.

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We start there, there's nothing there, there's

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something here.

145
00:06:08,980 --> 00:06:12,020
So we go to 3p6.

146
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And then the next thing we fill out is 4s2.

147
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So then we go to 4s2.

148
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And then what's the very next thing we fill out?

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00:06:21,389 --> 00:06:22,509
We have to go back to the top.

150
00:06:22,509 --> 00:06:24,789
We come here and then we fill out 3d.

151
00:06:24,790 --> 00:06:27,470
And then how many electrons do we have left to fill out?

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00:06:27,470 --> 00:06:28,720
So we're going to be in 3d.

153
00:06:28,720 --> 00:06:33,100


154
00:06:33,100 --> 00:06:34,530
And how many have we used so far?

155
00:06:34,529 --> 00:06:35,819
2 plus 2 is 4.

156
00:06:35,819 --> 00:06:37,649
4 plus 6 is 10.

157
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10 plus two is 12.

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18.

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00:06:41,040 --> 00:06:41,550
20.

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We've used 20, so we have 8 more electrons to configure.

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And the 3d subshell can fit the 8 we need, so we have 3d8.

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00:06:51,949 --> 00:06:54,129
And there you go, you've got the exact same answer that we

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00:06:54,129 --> 00:06:56,670
had when we used the first method.

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Now I like the first method because you're looking at the

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00:06:58,769 --> 00:07:01,089
periodic table the whole time, so you kind of understand an

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intuition of where all the elements are.

167
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And you also don't have to keep remembering, OK, how many

168
00:07:07,259 --> 00:07:09,259
have I used up as I filled the shells?

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Right?

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Here you have to say, I used two, then I used two more.

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And you have to draw this kind of elaborate diagram.

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Here you can just use the periodic table.

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And the important thing is you can work backwards.

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Here there's no way of just eyeballing this and saying,

175
00:07:21,230 --> 00:07:24,920
OK, our most energetic electrons are going to be 3d8,

176
00:07:24,920 --> 00:07:28,930
and our highest energy shell is going to be 4s2.

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There's no way you could get that out of this without going

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00:07:30,819 --> 00:07:34,329
through this fairly involved process.

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But when do you use this method, you can immediately

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say, OK, if I'm worried about element Zr, right here.

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00:07:44,620 --> 00:07:47,790
If I'm worried about element Zr.

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I could go through the whole exercise of filling out the

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entire electron configuration.

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But usually the highest shell, or the highest energy

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00:07:53,800 --> 00:07:55,780
electrons, are the ones that matter the most.

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00:07:55,779 --> 00:08:00,579
So you immediately say, OK, I'm filling in 2d there, but

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00:08:00,579 --> 00:08:03,359
remember, d, you go one period below.

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So this is 4d2.

189
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Right?

190
00:08:05,550 --> 00:08:06,639
Because the period is five.

191
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So you say, 4d2.

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00:08:07,889 --> 00:08:10,919


193
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And then, before that, you filled

194
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out the five s2 electrons.

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00:08:14,949 --> 00:08:18,009


196
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And then you could keep going backwards.

197
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And you filled out the 4p6.

198
00:08:20,660 --> 00:08:23,780


199
00:08:23,779 --> 00:08:31,449
And then, before you filled out the 4p6, then you had 10

200
00:08:31,449 --> 00:08:32,389
in the d here.

201
00:08:32,389 --> 00:08:33,399
But what is that?

202
00:08:33,399 --> 00:08:35,819
It's in the fourth period, but d you subtract one from it, so

203
00:08:35,820 --> 00:08:37,620
this is 3d10.

204
00:08:37,620 --> 00:08:39,889
So 3d10.

205
00:08:39,889 --> 00:08:41,909
And then you had 4s2.

206
00:08:41,909 --> 00:08:43,139
This is getting messy.

207
00:08:43,139 --> 00:08:43,928
Let me just write that.

208
00:08:43,928 --> 00:08:46,919
So you have 4d2.

209
00:08:46,919 --> 00:08:48,399
That's those two there.

210
00:08:48,399 --> 00:08:49,799
Then you have 5s2.

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00:08:49,799 --> 00:08:52,919


212
00:08:52,919 --> 00:08:55,870
Then we had 4p6.

213
00:08:55,870 --> 00:08:57,129
That's over here.

214
00:08:57,129 --> 00:08:58,830
Then we had 3d10.

215
00:08:58,830 --> 00:09:02,930
Remember, 4 minus 1, so 3d10.

216
00:09:02,929 --> 00:09:04,659
And then you had 4s2.

217
00:09:04,659 --> 00:09:06,639
And you just keep going backwards like that.

218
00:09:06,639 --> 00:09:08,620
But what's nice about going backwards is you immediately

219
00:09:08,620 --> 00:09:11,310
know, OK, what electrons are in my highest energy shell?

220
00:09:11,309 --> 00:09:14,449
Well I have this five as the highest energy shell I'm at.

221
00:09:14,450 --> 00:09:17,320
And these two that I filled right there, those are

222
00:09:17,320 --> 00:09:20,850
actually the electrons in the highest energy shell.

223
00:09:20,850 --> 00:09:22,480
They're not the highest energy electrons.

224
00:09:22,480 --> 00:09:23,009
These are.

225
00:09:23,009 --> 00:09:25,279
But these are kind of the ones that have the highest

226
00:09:25,279 --> 00:09:28,029
probability of being furthest away from the nucleus.

227
00:09:28,029 --> 00:09:29,779
So these are the ones that are going to react.

228
00:09:29,779 --> 00:09:31,399
And these are the ones that matter for

229
00:09:31,399 --> 00:09:33,449
most chemistry purposes.

230
00:09:33,450 --> 00:09:36,180
And just a little touchpoint here, and this isn't covered a

231
00:09:36,179 --> 00:09:39,199
lot, but we like to think that electrons are filling these

232
00:09:39,200 --> 00:09:40,780
buckets, and they stay in these buckets.

233
00:09:40,779 --> 00:09:44,100
But once you fill up an atom with electrons, they're not

234
00:09:44,100 --> 00:09:46,009
just staying in this nice, well-behaved way.

235
00:09:46,009 --> 00:09:48,980
They're all jumping between orbitals, and mixing together,

236
00:09:48,980 --> 00:09:51,330
and doing all sorts of crazy, unpredictable things.

237
00:09:51,330 --> 00:09:54,750
But this method is what allows us to at least get a sense of

238
00:09:54,750 --> 00:09:57,350
what's happening in the electron.

239
00:09:57,350 --> 00:10:00,440
For most purposes, they do tend to react or behave in

240
00:10:00,440 --> 00:10:03,500
ways that these orbitals kind of stay to themselves.

241
00:10:03,500 --> 00:10:06,220
But anyway, the main point of here is really just to teach

242
00:10:06,220 --> 00:10:08,230
you how to do electron configurations, because that's

243
00:10:08,230 --> 00:10:10,710
really useful for later on knowing

244
00:10:10,710 --> 00:10:11,629
how things will interact.

245
00:10:11,629 --> 00:10:14,125
And what's especially useful is to know what electrons are

246
00:10:14,125 --> 00:10:15,519
in the outermost shell, or what

247
00:10:15,519 --> 00:10:16,769
are the valence electrons.

248
00:10:16,769 --> 00:10:17,787