In the preferred Lewis structure of carbon monoxide, which formal charges do the atoms carry?

Core Concept

CO has 10 valence electrons, and the only arrangement satisfying both octets is a triple bond with one lone pair on each atom. Formal charge equals valence electrons minus nonbonding electrons minus half the bonding electrons, giving carbon 4 - 2 - 3 = -1 and oxygen 6 - 2 - 3 = +1. No 10-electron structure achieves both octets and zero charge, since the zero-charge double bond leaves carbon two electrons short. A full octet matters more than placing the negative charge on the more electronegative atom, so this structure wins.