Number of pi bonds?

Question

i'm stuck on a chem problem that i have been looking at for about 30 min. If anyone can help that would be greatly appreciated!(Please explain why too!)

Identify the hybridization of the carbon atom(s) in CO3-2

Also give the number of π bonds in the molecule or ion

Answer 1

you want to draw the lewis structure.
Carbon has 4 bonds around it, so no formal charge there.
But you only have 3 oxygens, so one of them is double bonded. The other two have a formal charge each of -1. This makes the a -2 charge on the whole molecule. Now you can find the hybridization on the carbon. How many electron domains does it have? Any lone pairs that will affect the normal geometry?

If there were 4 e- domains but you had one lone pair, it would have three bonds pushed down by the lone pair. So it wouldn't be tetrahedral but trigonal pyramidal. If no lone pairs, you can treat like a regular geometry.

If there is a double bond, it is made up by one sigma and one pi bond.
A triple bond has one sigma and two pi bonds.

Answer 2

The hybridization is sp2. The Lewis structure is O=C<(O2)=. The structure is planar. The number of pi-bonds is one. Of course, the pi-bonds skitter around the O atoms by resonance.