Question

What is the lewis structure of CO3^2-

Answer 1

2- CO

m

Answer 2

The answer above is almost correct, except for the fact that SO3^2- is NOT trigonal planar. It will be tetragonal due to the extra lone pair on Sulfur.

It is hard to draw in a text editor by I 'll try to explain the structures.

a: SO3^2-:
Sulfur in the center. It attaches to 1 oxygen atom through a double bond. This one oxygen atom will have 2 lone pairs. The sulfur also attaches to the other 2 oxygen atoms through a single bond. These 2 oxygen atoms each have 3 lone pairs. Each of these 2 oxygen atoms has a formal negative charge. Finally there is a lone pair on the sulfur.

b SO4^2+:
Sulfur in the middle again. It attaches to 2 oxygen atoms through double bonds. Each of these oxygen atoms have 2 lone pairs each. The sulfur also attaches to 2 more oxygen atoms through single bonds. Each of these 2 oxygen atoms have 3 lone pairs each. These last 2 oxygen atoms have a formal negative charge.

c NO2^-:
Nitrogen in the middle, attached to 1 oxygen atom through a double bond. This oxygen atom has 2 lone pairs. Attached to the other oxygen atom through a single bond. This oxygen atom has 3 lone pairs and a formal negative charge. Finally there is a lone pair on the nitrogen.

d: CO3^2-:
This is identical to a: SO3^2-, except replace the sulfur with carbon. The final lone pair (on sulfur) will be missing:
Carbon in the center. It attaches to 1 oxygen atom through a double bond. This one oxygen atom will have 2 lone pairs. The carbon also attaches to the other 2 oxygen atoms through a single bond. These 2 oxygen atoms each have 3 lone pairs. Each of these 2 oxygen atoms has a formal negative charge.

Answer 3

Thanks so much for the explanation. I really understood why the CO3^2- has an ideal structure. Two electrons are added, one to each oxygen, therefore each of them is left with a formal charge -1. That's always better than adding electrons to carbon, because oxygen is more electronegative.