VSEPR theory
The molecule SO3 is trigonal planar. As predicted by VSEPR theory, its structure belongs to the D3h point group. The sulfur atom has an oxidation state of +6 and a formal charge of 0. The S-O bonding is delocalized with all three S-O bond lengths equal at 1.42 Å. The electrical dipole moment of gaseous sulfur trioxide is zero.