How to calculate the bond order of carbonate ion?

Dear barnita,

Consider the carbonate ion, CO₃^2-

carbon (C) has four valence electrons x 1 carbon = 4 e^-
oxygen (O) has six valence electrons x 3 oxygens = 18 e^-
The ion has an overall negative two charge so we add 2 e^- to give a total of 24 e^- to be placed in the Lewis structure.

This affords a bond order for the carbon - oxygen bond of 1 1/3. (4 bonds averaged over three structures.)

Approved