molecular orbital theory

Molecular Orbital Theory was initially proposed by Hund and Mulliken in 1932 and was later on developed by Lennard Jones and Coulson. The following are the postulates:

· According to the theory a new orbital is formed by the combination of atoms such as a covalent bonding formation. In other words n number of atomic orbitals combine with n number of molecular orbitals. A 1s orbital can combine with a another 1s orbital and not a 2s orbital.

· Similar to filling atomic orbitals, the molecular orbitals are filled using Aufbau principle. First the electrons are filled in the molecular orbialts of lower energy and gradually to molecular orbitals of higher energies.

· Unless there is complete filling of molecular orbitals pairing of electrons does not occur(Hund’s rule).

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Vasantha Sivaraj,

askIITians faculty.