The formation of certain molecules involving Carbon, Boron, Beryllium etc. cannot be explained satisfactorily on the basis of VSEPR (Valence Shell Electron Pair Repulsion) Theory. Hence, a new concept called hybridization is developed to explain the shape of these molecules and also shape and bonding in other molecules adequately.
Hybridization is the process of mixing of dissimilar orbitals of the same atom to give rise to equal number of a new set of orbitals having same energy content and shape.
Types of Hybridization
On the basis of the types and the number of orbitals involved, hybridization can be categories:
1. sp hybridization
The mixing or combination of one ‘s’ and one ‘p’ orbital to form two ‘sp’ hybrid orbitals is known as sp hybridization. The two sp hybrid orbitals are oriented in opposite manner to each other with bond angle 180o. Each hybrid orbital consists of a bigger and a smaller lobe.
Formation of BeF2
The electronic configuration of central atom Be is 1s22s2. During hybridization, one of the electron is first excited to p orbital with the absorption of energy. And these two half filled orbitals undergo sp hybridization to form two sp hybrid orbitals which combine with two F atoms to form BeF2.
2. sp2 hybridization
The combination of one ‘s’ and two ‘p’ orbitals to form three sp2 hybrid orbitals is called sp2 hybridization. The three hybrid orbitals are oriented towards the corners of a triangle with bond angle 120o. For example:
Formation of BF3
3. sp3 hybridization
The combination of one ‘s’ orbital and three ‘p’ orbitals to form four sp3 orbitals is called sp3 hybridization. The four hybrid orbitals are oriented towards the four corners of a tetrahedron with bond angle 109.5o. For example:
Formation of CH4