The carbon dioxide (CO₂) molecule consists of carbon (C) with four valence electrons and an oxygen (O) atom with six valence electrons. The carbon atom shares a double covalent bond with each oxygen atom. Its most stable Lewis structure is shown below.

O=C=O

To calculate the formal charge of CO₂, let us determine the formal charges on C and O atoms.

Carbon

V = 4, N = 0, B = 8

Therefore,

q_f = 4 – 0 – 8/2 = 0

The formal charge on C in CO₂ is zero.

Oxygen 1 and Oxygen 2

V = 6, N = 4, B = 4

Therefore,

q_f = 6 – 4 – 4/2 = 0

The formal charge on O in CO₂ is zero.

The net formal charge is: 0 + 2 x 0 = 0

The formal charge of CO₂ is zero.