Molecular Orbital Theory

In chemistry, Molecular orbital (MO) theory is a method for describing the electronic structure of molecules using quantum mechanics. Electrons are not assigned to individual bonds between atoms, but are treated as moving under the influence of the nuclei in the whole molecule.

MO theory can more accurately explain the bonding in the structures with resonance. Such as N2+

1. Intro

Simple example below, shows MO for H2 molecule and why He2 cannot exist

2. MO for diatomic moleculs

For 2π there are two diffrent MO diagrmas for (O2, F2) and (B2, C2, N2):

For O2 and F2:




For B2, C2, N2:

3. HOMO and LUMO

HOMO - highest occupied molecular orbital
LUMO - lowest unoccupied molecular orbital