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Hybridization of Atomic Orbitals

Hybridization is a theoretical concept which has been introduced to explain some structural properties such as shapes of molecules or equivalency of bonds, etc., which cannot be explained by simple theories of valency.


According to this concept, valence orbitals of the atom intermix to give rise to another set of equivalent orbitals before the formation of bonds. These orbitals are called hybrid orbitals or hybridized orbitals and the phenomenon is referred to as hybridization. Thus, hybridization may be defined as the phenomenon of intermixing of atomic orbitals of slightly different energies of the atom (by redistributing their energies) to form new set of orbitals of equivalent energies and identical shape. See box item to understand the concept of hybridization.



Some salient features of hybridization are:

The orbitals taking part in hybridization must have only a small difference of energies.

  • The hybridized orbitals have equivalent energies and identical shapes.
  • The number of hybrid orbitals is equal to the number of orbitals taking part in hybridization.
  • Both half-filled as well as completely filled orbitals of valence shell can take part in hybridization. It implies that promotion of electrons from lower sub-shell to higher sub-shell is not an essential condition prior to hybridization.
  • ┬áThe hybrid orbital has electron density concentrated on one side of the nucleus, i.e., it has one lobe relatively larger than the other shown as follows.

Representation of a hybrid orbital.

  • The hybrid orbitals can form stronger bonds as compared to the unhybridized or pure atomic orbitals because they can undergo more effective overlap.
  • ┬áThe hybrid orbitals are directed in space in some preferred directions so as to have minimum repulsive interactions and attain maximum stability. Thus, the type of hybridization controls the geometry of molecule.