A trigonal-planar molecule, PX3, has three different substituents: F, Cl, and Br. The P–X bond lengths can be treated as identical, and the substituents are arranged 120° apart in the order P–F, P–Cl, and P–Br around the plane of the molecule.
(a) Rank the three P–X bonds from smallest to largest bond-dipole magnitude.
(b) Justify the ranking in part (a) by referring to periodic trends in electronegativity within the halogen group.
(c) Using vector addition of the three individual bond dipoles, predict the approximate direction of the net molecular dipole moment within the plane of the molecule. Clearly state toward which substituent the overall dipole points and explain your reasoning.