Ionisation energy of nitrogen is greater than that of oxygen because nitrogen has

A. High bond dissociation energy

B. Smaller atomic radius

C. Stable half filled 2p sub level

D. High nuclear charge

Answer: Option C

Solution(By Examveda Team)

Nitrogen has a half filled orbital. On the other hand, since Oxygen is already unstable relative to Nitrogen, by losing one electron it attains a stable half filled orbital. So oxygen undergoes ionisation at a relatively lower energy. This is why nitrogen has a higher ionisation energy than oxygen.