In my AP chem test, I had a question that asked me to find the bond order of the ion $\ce{SO3^2-}$.
To draw the lewis structure, I determined that there are a total of $6+3\cdot 6+2=26$ electrons, and the sulfur had $\frac{26-8\cdot3}{2}=1$ lone pairs.
When we measure formal charges, every atom has one, and I have been told that this means the given lewis structure is inherently unstable and will attempt to form additional bonds. I use a pair on the oxygen to form a double bond, which eliminates the formal charges on the oxygen and sulfur, giving me the three (what i presume to be more stable) resonance structures
Hence the bond order is $\frac43$.
However, my teacher told me this was wrong. Apprently, due to the octet rule, the first lewis structure is the correct one where there are just three single bonds, and it's actually more stable since it satisfies the octet rule.
This makes me confused though. Which is the actual correct lewis structure (well, correct in a sense that the majority of the resonance structures exist in that form. I know that at least some aka a minor minor amount of $\ce{SO3^2-}$ would probably exist in the single bond form) that you would find bond order with?
I think this in the end comes down to whether or not formal charge or octet rule takes precedence, and based on everything I can find online, it seems formal charge does. So why does my chemistry teacher insist that the octet rule does? Am I misunderstanding something?