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What is the Valence Bond Theory and Molecular Orbital Theory (VBT and MOT)? What are the Difference between them?

Answer:

Valence Bond Theory and Molecular Orbital Theory (VBT and MOT)

Valence bond theory (VBT)

1. After the bond formation, the combining atoms in a molecule retain their identity.
2. Bonding is explained with the help of atomic orbitals.
3. Only the half‐filled atomic orbitals of the valence shell take part in bond formation.
4. The concept of resonance is applicable only to valence bond theory.
5. It fails to explain the paramagnetic character of O2 molecule.
6. This theory finds difficulty in explaining the stability of one and three electron bond’s having unpaired electrons.
7. VBT fails to explain the formation of O2+ and O2- ions from O2 has the stable octet.

Molecular orbital theory (MOT)

1. After the bond formation, the combining atoms in a molecule loose their identity.
2. Bonding is explained with the help of molecular orbitals.
3. It considers all the electrons in the given atoms for the prediction of number of bonds per atom.
4. Resonance has no role in molecular orbital theory.
5. It explain the paramagnetic character of O2 molecule.
6. The formation of one electron bond and three electron bonds can be easily explained by MOT.
7. MOT can explain the formation of O2+ and O2- ions from O2 .