Question

Between SO2 and SO4 2-, which one has shorter sulfur oxygen bond length since it has same bond order?

Answer 1

Bond length of $SO_2$ $(14.29 \ pm)$ is less than that of $SO_4^{2-}$ $(15.2 \ pm)$ because $SO_2$ has perfect double bond,while $SO_4^{2-}$ has partial double bond because of resonating structure.