Problem: Which of the following compounds or ions exhibit resonance?a. O3 b. CNO-c. AsI3d. CO32-e. AsF3

a. O₃ 

O → Group 6A → 6 val. e^- x 3

The electrons in the double bond (O=O) can move to the other O-O bond. 

O₃ exhibits resonance.

b. CNO^-

C → Group 4A → 4 val. e^-

N → Group 5A → 5 val. e^-

O → Group 6A → 6 val. e^-

- charge → +1 electron

The electrons in the double bonds can move about while maintaining the overall charge of the ion equal to -1.

CNO^- exhibits resonance.

c. AsI₃

As → Group 5A → 5 val. e^-

I → Group 7A → 7 val. e^- x 3

ideal structure → no pi electrons that can move about

AsI₃ do not exhibit resonance.

d. CO₃^2-