The Lewis structure of Carbonic Acid (H₂CO₃) is given below. In structure it is shown that carbon has a double bond with one oxygen atom and two single bonds with hydroxyl groups.
Formal Charge;
Formal charge is caculated as,
Formal charge = # of valence e⁻ - [# of lone pair of e⁻ + 1/2 # of bonded e⁻]
Formal charge on Carbon;
Formal charge = 4 - [ 0 + 8/2]
Formal charge = 4 - [4]
Formal charge = Zero