The lowest-octet Lewis structure is ⁻C≡O⁺. Carbon and oxygen share a triple bond, each atom has one lone pair, and the formal charges are unusual but required.
A single bond alone cannot give both atoms octets.
Form a triple bond.
Six electrons are shared between the atoms.
Add one lone pair to each atom.
This uses the remaining four electrons.
Calculate formal charges.
Carbon is −1 and oxygen is +1; the molecule remains neutral overall.
Why the charges look reversed
Lewis formal charge is electron bookkeeping, not a direct map of partial charge. The octet-satisfying structure assigns carbon −1 and oxygen +1 even though oxygen is more electronegative.
Electron check
The triple bond contains 6 electrons and the two lone pairs contain 4, totaling 10.
Common mistakes
Drawing C=O with only a double bond and incomplete octets.
Omitting formal charges because the molecule is neutral.
Putting both lone pairs on oxygen.
Assuming formal charge and partial charge are the same concept.