Question

Which of the following would need resonance structures?
SO2
CH4
O2
CO3-2

Answer 1

the answer is CO₃²⁻
the structure of SO2 does not permit resonance, ··O≡S≡O··
CH4 is a saturated compound. Saturated compounds don't resonate.
O2 is a gas that is already in its stable form and so can't resonate.