structure of SO2 and SO3

[Andie Jian 1D]

For 7th edition 6A.15 and 6.5, the questions ask you to draw the structures of SO2 and SO3 respectively. I thought having all of the oxygens with double bonds would be the most stable structure, providing the lowest formal charges. However, the answers show SO2 with 1 double and 1 single bond, and SO3 with 1 double bond and 2 single bonds. Why is this?

[Matthew Mar 1J]

The book might be referring to a sulfite (SO3 -2) ion, where having one double bond and two single bonds would account for the -2 charge on the molecule. I'm not really sure about the SO2 because I'm pretty sure sulfur dioxide is supposed to be neutral.

[Kyither Min 2K]

I may be wrong but i believe that the structure of SO2 and SO3 are like that because they have resonance and resonance makes a structure a lot stronger and stable so resonance is preferred!