Ionisation potential of O is less than that of N-explain.

Explanation

The reason for such a difference may be explained on the basis of their electronic configuration.

2p-orbital of outermost shell of N-atom, being half. Filled, its electronic configuration is highly stable, so, a large amount of energy is required to form `N^(+)` ion by removal of 2p-electron. on the other hand, formation of `O^(+)` ion by removal of one electron from partially filled 2p-orbital requires less energy. since, 2p-orbital of `O^(+)` ion being half-filled, the electronic configuration assumes stability. hence, oxygen has lower ionisation potential than nitrogen.