Question

So3 has zero dipole moment​

Answer 1

SO3 is a planar molecule with three bond angles 120 degrees apart. The individual dipole moments of S-O bond cancel out each other due to which the dipole moment of SO3 molecule is zero.

Answer 2

SO3 is a trigonal planar molecule, which can be derived from its Lewis structure. Each sulfur-oxygen bond is polar from S to O, but the three bonds are equally polar and are pointed in symmetrical opposition so that they cancel. The SO3 molecule has a dipole moment of zero.