A non-polar molecule is SO3. Three S-O bonds and no non-bonding electron pairs are present in the molecule. Trigonal planar geometry produces a non-polar molecule.
A difference in electronegativity leads to polarity. Because it is more electronegative than sulphur, oxygen more strongly draws electrons. The oxygen in the S-O bond has an unequal distribution of electrons, which gives it a negative charge and gives the bond polarity.
The three S-O bonds are situated 120 degrees apart from one another in the same plane. The polarities are cancelled as a result of the trigonal planar geometry, and a non-polar molecule is created.