Answer to Question #92396 in General Chemistry for Tj

Question

Using electronegativity values, determine bond polarities and the net dipoles in a molecule of SO3 and indicate if the molecule will be polar.

Answer 1

A molecule of SO₃ possesses D_3h point group symmetry. It is actually an equilateral triangle, where the sulfur atom is in the middle and three coplanar oxygen atoms are in the vertices. Further, the relative pauling electronegativity of sulfur is 2.5, while that of oxygen is 3.5 relative units. Thus, the sulfur atom would have a positive charge and oxygen - negative. According to this, the dipole moment of each S-O bond in the SO₃ molecule will be directed from sulfur to oxygen:

However, the molecule in whole will not be polar (gratefully to its symmetry) i.e. three dipole moments act against each other, resulting in a zero net dipole moment.