00:01
All right, in this question, we are drawing a bunch of leoist structures.
00:05
So let's get started.
00:07
First up, we have cf4.
00:12
Cf.
00:15
And the first step to drawing the leoose structure is to calculate out the valence electrons that we need.
00:21
So we have four for the carbon and seven for each of the fluorines, and we have four fluorines.
00:30
So that means we have a total of 30.
00:34
32 electrons that we have to distribute.
00:37
We'll start by putting the carbon in the center.
00:40
Why did i put the carbon in the center? carbon is the least electronegative of the atoms in this group.
00:48
Between carbon and fluorine, it's the least electronegative.
00:52
We also know that carbon likes to form four bonds.
00:57
So in general, when you see a carbon, you can expect it to probably be in the center of the structure.
01:05
So let's draw out our fluorines.
01:16
And let's just take a moment to look at where we are.
01:20
So we have four bonds.
01:22
This carbon is bonded to each of the fluorines.
01:25
Each bond takes up two electrons.
01:28
So that's minus eight right there.
01:31
That leaves us with 24 electrons left to distribute.
01:36
Now, we'll start with this fluorine on the left.
01:39
This fluorine has two electrons.
01:43
And it's trying to get to 8 to satisfy the act that rule.
01:48
So let's try giving it 6 valence electrons, and now this fluorine has access to 8.
01:56
We'll do the same thing with each of these fluorines, and let's talk where we are with the math.
02:08
I just gave 6 of these electrons to this fluorine, 6 to that one, 6 to that one, and 6 to that one.
02:18
So that equals 20 ,000.
02:20
Four electrons i just used up.
02:23
So that should use up our remaining electrons.
02:29
And we can do one more thing to double check.
02:33
We've already checked that each of these florenes has eight.
02:36
We know that this carbon has eight.
02:38
So all the atoms have access to eight electrons.
02:41
And let's just double check our total.
02:46
We've got six electrons from all of the free electrons.
02:51
And then we've got around this top fluorine.
02:54
And then we've got two in the bond.
02:56
So this group has eight electrons if we include this bond.
03:01
And obviously each of these also have eight.
03:07
And when we do eight times four, it equals 32.
03:11
So therefore we know that this is probably the correct lewis structure for cf4.
03:18
Later on, you can do one more verification step by calculating formal charges, but the short answer is this is the correct structure.
03:27
Okay, moving on.
03:29
Our next structure is ch3 cl.
03:35
So ch3cl.
03:39
We'll start by calculating out our electrons who've got four for the carbon, one for each of the hydrogen, and seven for the chlorine.
03:48
That means we have 14 total electrons.
03:51
We'll put carbon in the center because it's the least electronegative.
03:55
We are going to add the three hydrogens, and we're going to add a chlorine.
04:01
And this chlorine only has two electrons right now.
04:07
So let's try adding six more to complete the octet.
04:14
Now let's calculate if we used up all of our electrons.
04:18
Six right here.
04:22
It's got eight left over.
04:25
And we have four bonds around this carbon.
04:28
We've got one, two, three, four.
04:31
Each bond takes two electrons.
04:35
So, and we have four of them.
04:37
So that uses of eight electrons.
04:40
So in total, we've just used up all 14 of our valence electrons.
04:44
So this is the lewis structure for ch3cl.
04:50
Moving on, we have sicl -s -c -l -s -c -l -2.
05:04
So silicon is the least electron negative of the group.
05:09
So it's going to go in the center.
05:11
We'll put a hydrogen on one side, a hydrogen over here, a chlorine over here, and a chlorine over here.
05:24
And we're going to fill up the octets for the chlorines, and we're going to check our work.
05:33
So silicon has four electrons because it's in the same group as carbon.
05:39
It's group 4a.
05:41
Chlorine has 7 and we have two of them.
05:46
And we've got 2 hydrogen.
05:48
Now i'm just going to say 2 for that.
05:51
So that equals, let's see, this is 14 plus 4 is 18 plus 2 is 20.
05:57
We've got 20 total electrons.
06:00
And let's see how many we have in our structure.
06:04
So over here we have 8.
06:08
Over here we have 8 because we have 6 six non -bonded electrons and then plus two in the bond.
06:21
And then we have two over here.
06:25
And we have two over here.
06:27
So 8 plus 2 plus 2 plus 8 is equal to 20.
06:32
And we should be good to go.
06:35
And let's just check our silicon.
06:38
So the silicon has four bonds to it...