Question

Why first ionization enthalpy of nitrogen is more than oxygen?

Answer 1

Since $N$ ${1s}^2$ ${2s}^2$ ${2p}^3\to$ half filled

$O$ ${1s}^2$ ${2s}^2$ ${2p}^4\to$ partially filled

Stability$=$ half-filled$>$ partially filled

Hence $IE=N>O.$