# What is the formal charge of carbon atom in the lewis structure of carbonyl sulfide (OCS)?

To a first approx. the Lewis structure of carbonyl sulfide is the same as that of carbon dioxide. The formal charge of $C$ is thus ZERO.
Given an $O = C = O$, or $S = C = O$ Lewis structure, there are 8 bonding electrons around carbon, 4 of which this atom claims. And thus with 2 inner core electrons, the 6 electrons balance the nuclear charge to give a neutral carbon centre. Of course all the atoms in this molecule are formally neutral.
The $C = S$ bond length is approx. $1.6 \times {10}^{-} 10 \cdot m$, the which is shorter than a regular $C - S$ bond, approx. $1.8 \times {10}^{-} 10 \cdot m$.