Valence Bond Theory (VBT)

Molecular Orbital Theory (MOT)

Bonds are localized to two atoms not molecule.

Bonds are localized to two atoms as well as molecule.

Valence orbital theory was first proposed by W.Heitler and F.London in 1927.

Molecular orbital theory was proposed by F. Hund and R.S. Mulliken in 1932.

Resonance plays an important role in this theory.

There is no place of resonance in this theory.

There is no explanation of paramagnetic character of oxygen.

Satisfactory explanation of paramagnetic character of oxygen.

Calculations are simpler.

Calculations are very tedious.