(a) Explain sigma and pi bonds with suitable examples,
(b) A pi bond cannot be formed in the absence of sigma bond. Discuss.

Explanation

The strength of a covalent bond depends upon the extent of the overlap. Greater the overlap, stronger is the bond. A sigma bond is formed by the exial overlap of the orbitals while pi bond by their sidewise or lateral overlap. Since the axial overlap is more effective than the sidewise overlap, greater energy is will be released in the axial overlap as compared to sidewise overlap. Therefore, sigma bond a stronger that the pi bond.