Tip:
Highlight text to annotate it
X
This is the COS Lewis structure: Carbonyl Sulfide. For Carbonyl Sulfide we have 4 +
6 + 6 valence electrons, for a total of 16 valence electrons for the COS molecule. Carbon
is the least electronegative. That'll go at the center, and we'll put the Oxygen on one
side, and the sulfur on the other. We'll start by putting two electrons between the atoms
to form chemical bonds. We'll go around the outside: we'll use 2, 4, 6, and 16 valence
electrons. So we've used all 16 of the valence electrons we started with. this Sulfur here
has 8, so it has an octet; and the Oxygen has 8--it has an octet. Howver, the Carbon
in the center only has 4 valence electrons, so it doesn't have an octet. To solve this
problem, we can take two valence electrons here, from the Sulfur, and move them inside
to form a double bond. We're still using 16 valence electrons, but now we have 8 valence
electrons here, on the Sulfur, and the Carbon has 6. We're getting closer. Let's share these
two here from the Oxygen with the Carbon. So now, by sharing, we have 8 on the Oxygen
and 8 on the central Carbon. Sulfur still has 8. And we're only using 16 valence electrons.
That makes this the Lewis structure for COS. You might ask why I didn't form a triple bond
between the Oxygen and Carbon, or a Sulfur and Carbon. The reason is that Oxygen and
Sulfur don't normally form triple bonds. If I did that and checked my formal charges,
I'd find that my formal charges would be +1 and -1 on the Oxygen and Sulfur. So, that
wouldn't be the best Lewis structure for COS. Formal charges should be as close to zero
as possible. In the case with this structure here, they're all zero for each of the atoms.
This is Dr. B. with the Lewis structure for COS, and thanks for watching.