Question

Intuitively, why is it that when the HOMO-LUMO gap is small then the bonding molecular orbital produced is of significantly lower energy?

Answer 1

Having done some thinking on my own, my explanation is that the closer the energy levels of the HOMO and LUMO, the greater the extent of orbital overlap. Is this logical? More importantly, is it accurate?

Answer 2

Explanation:

the electrophilic and nucleophilic species would produce bonding molecular orbitals much lower in energy, giving rise to greater stabilisation upon electron population.

• I would like an intuitive explanation, not a mathematical one (such as by the Klopman-Salem equation).

• Having done some thinking on my own, my explanation is that the closer the energy levels of the HOMO and LUMO, the greater the extent of orbital overlap.