From a consideration of the lewis structure of the thiocyanate ion, scn-, in which carbon has a double bond with both the sulfur and nitrogen atoms, the formal chareges on the sulfur, carbon, and nitrogen atoms are, respectively,

Formal charges on S, C and N atoms are 0, 0 and -1 respectively.

Explanation:

Formal charge on an atom = (no. of valence electron of the atom) - (no. of unshared electrons on the atom) - (no. of covalent bond attached directly with the atom)

From the Lewis structure given below-

Formal charge on S = (6) - (4) - (2) = 0

Formal charge on C = (4) - (0) - (4) = 0

Formal charge on N = (5) - (4) - (2) = -1

So, formal charges on S, C and N atoms are 0, 0 and -1 respectively.