Question

Distinguish between sigma and pi bond?

Answer 1

See below.

Explanation:

Simplistically sigma bonds are single covalent bonds e.g. in organic compounds like methane `CH_4` . Pi bonds are double or triple covalent bonds so again in organic compounds like ethene and ethyne.

The different bonds form from being formed differently. Sigma bonds in alkanes form through `sp^3` hybrid orbital overlap. The pi bond in an alkene forms through `sp^2` hybrid orbital head on overlap plus the sideways overlap of unhydridised `p` orbitals on each of the carbon atoms creating the pi bond,. In Alkynes it is `sp` hybrid orbitals overlapping and 2 unhybridised `p` orbitals overlapping to form 2 pi orbitals to complete the triple bond.