Chemistry: Molecular Approach (4th Edition)

$H_2CS$ is the better structure because the formal charge on $C$ and $S$ is zero in this structure.
We know, formal charge = no. of valence electrons - (no. of nonbonding electrons + 1/2 no. of shared electrons) In $H_2CS$, Formal charge on carbon = 4 - (0+ 1/2*8) = 0 Formal charge on sulfur = 6 - (4+ 1/2*4) = 0 In $H_2SC$, Formal charge on carbon = 4 - (4+ 1/2*4) = -2 Formal charge on sulfur = 6 - (0+ 1/2*8) = 2 $H_2CS$ is the better structure because the formal charge on $C$ and $S$ is zero in this structure.