Why is CO2 non polar?
Carbon dioxide is non-polar because of the symmetry of its bonding. The electronegativity difference between carbon and oxygen is 1.0, which makes the bonds polar. However, the two polar bonds are at 180 degrees to each other so the dipoles cancel out. (Dipoles are regions of charge separation due to unequal sharing of electrons.)
The Lewis dot structure of carbon dioxide has carbon as the central atom, with double bonds to each of the two oxygen atoms. This completes the octet for carbon. Each oxygen atom has two non-bonding pairs of electrons. If you're familiar with hybridization, this is sp hybridization which results in a linear shape. If you're not familiar with hybridization, the idea is that the bonding and non-bonding electrons determine the shape of the molecule. The two double bonds are at 180 degrees because it's the maximum separation (they repel each other.)