Question

Discuss "Molecular Orbital Theory" by giving one example. Your explanation should include the comparison of this theory with hybridization and Lewis structures.

Answer 1

According to Molecular Orbital Theory (MOT), the nuclei of the two atoms lie at appropriate distance and all the atomic orbitals of one atom overlap with all the atomic orbitals of the other atom provided the overlapping orbitals are of same symmetry and of similar energy. It is a method of describing electronic structures of molecules using quantum mechanics. The Molecular orbital diagrams are drawn by filling in the electrons in the atomic orbitals and thus forming their respective molecular orbitals. An example of molecular orbital diagram of CO molecule is in the following image:

With the help of molecular diagrams, the bond order of molecules can be calculated.

The similarities between the MOT and VBT (hybridization) is that in the bond formation, the orbitals of the bonding atoms must overlap. The basic principles involved in the distribution of electrons are similar. An orbital, atomic or molecular, cannot have more than two electrons.

Though the basic principle involved is the same but MOT is considered superior to VBT because the latter could not explain the paramagnetic nature of oxygen.

Lewis structures are diagrams that represent the valence electrons of atoms within a molecule. These structures help in determining the valence electrons of atoms within molecules and presence of lone pairs, if any.