Question

What is the formal charge of ${NO}_2^{-}$?

Answer 1

Formal charge on atom in a molecule= (total no. of valence electrons in the free atom)- (total no. of non-bonding electrons)-1/2 (total no. of bonding electrons)

Formal charge on double bonded $O$ atom $=6–4–0.5\left(4\right)=0$

Formal charge on single bonded $O$ atom$=6–6–0.5\left(2\right)=-1$