試題詳解

30. The energy of the first triplet excited state is lower than that of the first singlet excited state for ethylene. What is the correct explanation for it?
(A) the more unpaired electrons the more stable a molecule
(B) only the singlet excited state has electron(s) in antibonding orbital(s)
(C) the triplet excited state has a larger bond order
(D) the wavefunction is antisymmetric with respect to electron interchange.
(E) Hund's rule requires that the electrons are filled parallel first.