Question

Can someone explain how I set up a molecular orbital diagram?

Answer 1

Hint The valence bond theory fails to explain some molecules' existence and does not tell the nature of paramagnetic or diamagnetic substances. Therefore in 1932 F. Hood and R.S. Mulliken gave a new concept molecular orbital theory.

Complete answer:
Molecular Orbital Theory is abbreviated as MOT which states that each individual atom tends to combine with each other and form molecular orbitals. Thus the electrons of an atom are present in various atomic orbitals associated with several nuclei. Hence to draw molecular orbital diagram we have to go through some important points:
1. Firstly choose the set of atomic valence orbitals i.e. that orbital which is in contact with each atom assumes that core orbitals do not interact in this.
2. Then calculate the relative orbital energies of the given molecule.
3. By combining the orbitals each of the two atomic orbitals interact with one other to produce one bonding and one anti-bonding molecular orbital.
4. Then the valence electrons present in them are equally distributed according to Aufbau Principle, Pauli Exclusion Principle and Hund’s rule in the molecular orbital diagram.
In this way we can draw a molecular orbital diagram.
Anti-bonding molecular orbitals weaken the bond between two atoms whereas non-bonding molecular orbitals do not affect the bond between two atoms.

Note: The number of molecular orbitals formed is always equal to the number of atomic orbitals combining with them and the shape of molecular orbitals formed depends upon the shape of the atomic orbitals which combine with each other.