Chemical Bondin...

Molecular orbital theory describes bonding in terms of the combination and arrangement of atomic orbitals to form molecular orbitals that are associated with the molecule as a whole.

The number of molecular orbitals formed is equal to the number of combining atomic orbitals. When two atomic orbitals combine, two molecular orbitals called bonding molecular orbital and anti-bonding molecular orbital are formed. The two atomic orbitals so formed by LCAO (Linear Combination of Atomic Orbitals) are in the same phase (bonding molecular orbital) or in different phase (anti-bonding molecular orbital). The energy of bonding molecular orbital is lower than that of the pure atomic orbital by an amount Δ, which is known as stabilization energy. The energy associated with antibonding molecular orbital is higher than that associated with pure atomic orbital by an amount Δ which is known as destablization energy. In bonding molecular orbitals the inter-electronic attraction is present whereas in anti-bonding molecular orbital we find an inter electronic repulsion.