Question

What is meant by hybridisation of atomic orbitals? Describe $sp,s{p}^2$ and $s{p}^3$ hybridixation with examples.

Answer 1

Hybridization is the phenomenon of intermixing of orbitals slightly different energies so as to redistribute their energies and to give new set of orbitals of equivalent energy and shape. The atomic orbitals taking part in hybridisation are called hybrid orbitals. These hybrid orbitals have minimum repulsion between their electron pairs and thus are more stable. Only orbitals of almost similar energies and belonging to same atom and ion under go hybridization. Th number of hybrid orbitals produced ie equal to the number of pure orbitals mixed during hybridization. The type of hybridisation indicates the geometry of the molecules. Only atomic orbitals participate in hybridisation. Electron's present in them do not take part.

(a) $sp$ hybridisation: The type of hybridisation involves the mixing of one $s$ and one $p$ orbital resulting in the formation of two equivalent $sp$ hybrid orbitals. Each $sp$ hybrid orbital has $50\%s-$ character and $50\%p-$character. Such a molecules in which the central atom is $sp-$hybridised and linked directly two other central atoms possesses linear geometry.

This type of hybridisation is also known as diagonal hybridisation. The bond angle is ${180}^o$.

(b) $s{p}^2$ hybridisation: In this hybridisation, there is involvement of one $s$ and two $p$ orbitals in order to form three equivalent $s{p}^2$ hybridized orbitals. The three hybrid orbitals so formed are oriented in a plane at maximum distance to form an angle of ${120}^o$ between the hybrid orbitals. The hybrid orbitals are oriented in a trigonal planar arrangement.

(c) $s{p}^3$ hybridisation: In this type of hybridisation, there is mixing of one $s-$orbital and three $p-$orbitals of the valence shell to form four $s{p}^3$ hybrid orbital equivalent energies and shape. There is $25\%s-$ character and $75\%p-$character in each $s{p}^3$ hybrid orbital. This hybridisation has tetrahedral geometry.