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

The correct answer is D. High nuclear charge.

The ionization energy of an atom is the energy required to remove an electron from an atom in its ground state. The higher the nuclear charge, the more strongly the electrons are attracted to the nucleus, and the more energy is required to remove them.

Nitrogen has a higher nuclear charge than oxygen, because it has one more proton in

its nucleus. This means that the electrons in nitrogen are more strongly attracted to the nucleus, and more energy is required to remove them.

The other options are incorrect.

• Option A is incorrect because bond dissociation energy is the energy required to break a chemical bond. It is not related to ionization energy.
• Option B is incorrect because atomic radius is the distance from the nucleus to the outermost electron shell. It is not related to ionization energy.
• Option C is incorrect because a stable half-filled 2p subshell is not a factor that affects ionization energy.