Ionization `"enthalpy"_(1) (IE)_(1)` of O is less then that of N-explain.

Explanation

In N, the 2p or orbitals are half-filled `(1s^(2)s^(2)2p_(x)^(1)2p_(y)^(1)2p_(z)^(1))` and more stable. Hence the `IE_(1)` of N is high. In `O(1s^(2)2s^(2)2p_(x)^(2)2p_(y)^(1)2p_(z)^(1))`, there are repulsions among the paired up 2p electrons, which lowers the I.E..