The pyramidalization and energies of inversion of group 15 :MR 3 (M = N, P, As, Sb, Bi) and group 14 •MR 3 molecules can also be predicted and rationalized using a second-order Jahn-Teller distortion treatment. The “parent” planar molecule possessing D 3h symmetry has frontier orbitals of a 2 ” (HOMO) and a 1 ’ (LUMO) symmetries. The pyramidalizing vibration mode has symmetry a 2 ”. The triple product yields the totally symmetric representation a 1 ’, indicating that the molecule will indeed pyramidalize into C 3v symmetry.