00:02
Hi there.
00:02
In this question, we have five elements for which we want to write the noble gas electron configuration and then state what period each element belongs in.
00:14
All right.
00:15
So our first one is lithium.
00:16
Looking at the periodic table, its atomic number is three.
00:19
So that means not only is it have three protons, but it also has three electrons.
00:25
Writing the noble gas configuration for this, we need to put the noble gas from the period before lithium in brackets.
00:32
So that would be helium.
00:33
And that takes care of the first two or the core electrons of lithium.
00:39
So then all we have left right is that valence electron, the 2s1.
00:44
All right, so this would then be in the second period of the periodic table.
00:58
Moving to our next element, we see it's oxygen on the periodic table.
01:02
Oxygen is atomic number 8.
01:05
It is in period 2.
01:08
I'm just going to write period 2 instead of the second.
01:10
Let's write period 2.
01:13
Therefore, we need to look at period one for the noble gas to put in the brackets, which is, again, helium.
01:21
So that takes care of the first two electrons.
01:23
Then we need to complete the configuration for the remaining six, the valence electrons.
01:28
Two of those will go in the 2s, and the remaining four will go in the 2p.
01:34
All right, so oxygen is in the second period or period two.
01:41
Letter c, we have copper.
01:46
All right, and we look at copper.
01:49
Its atomic number is 29.
01:57
Copper is a little bit of an exception to the outfow rule of filling.
02:02
But let's talk about that when we get there.
02:04
So since it's number 29, it has 29 protons and then 29 electrons.
02:10
And we see that copper is found in period 4.
02:17
Therefore, we need to look at the noble gas in period 3, and that is argon.
02:22
So this takes care of the first 18 electrons.
02:27
Then we see that copper is in the 3d.
02:32
In order to get to 3d, we typically need to fill up the 4s.
02:37
But don't write this down yet because it's not correct.
02:40
That would give us a 3d 9 to end up with 29 electrons...