OK, this is Dr. B.
We're going to do the Lewis structure for
CO2, Carbon dioxide.
On the periodic table, Carbon is in group
4, or 14 sometimes; and then Oxygen is in
group 6 or 16.
But we have two of them.
So let's multiply that together there: so
we have 12 plus 4, 16 total valence electrons.
Let's draw the structure.
Carbon is the least electronegative; that
means it's going to go at the center.
So we'll put the Carbon right here, and then
Oxygens on either side of that.
So now we want to draw some chemical bonds.
Let's put a pair of electrons between each
of these, so now they're bonded.
We've used four.
Then let's complete the octets on the outer
shell.
So, 4, 6, 8, 10, 12, 14, 16.
That looks pretty good: looks like it kind
of works out the way we want it to.
Let's check and see if we have octets.
This Oxygen here has 8.
This Oxygen here has 8.
They both have octets.
The Carbon only has 4 valence electrons, it
doesn't have an octet.
What we can do is, we can share electrons--these
nonbonding electrons out here between the
atoms there.
Now we have 2, 4, 6, 8; that Oxygen's OK.
The Carbon has 2, 4, 6.
Little bit closer.
Let's take some electrons over here and share
them on this side so that Oxygen has 8, we
still have 8 over here.
And now Carbon in the center has 2, 4, 6,
8.
So we've completed the octet.
And if you add them up, 2, 4, 6, 8, 10, 12,
14, 16, we've used 16 valence electrons.
That's all we had to start out with.
Let's clean that up there.
If we wanted to write this as a structural
formula, we could also do that and that would
look like this.
In this structural formula, the two lines
right here are the same as these two pairs
of valence electrons.
This is Dr. B., and thank you for watching.
