# What is the resonance structure for CO_3^-2?

$C {O}_{3}^{2 -}$ $=$ $\left(O =\right) C {\left(- {O}^{-}\right)}_{2}$
There are $4 + 6 + 6 + 6 + 2$ valence electrons, i.e. 12 electron pairs to distribute over 4 centres. Of course, the resonance structure features 3 regions of electron density around a central carbon, and thus a trigonal planar structure. The oxygen atoms are all equivalent, and each $C - O$ bond has partial double bond character.