Question

Ionization energy of nitrogen is greater than oxygen due to

• A. increased attraction of electron towards the nucleus
• B. extra stability of half filled ‘p’ orbital
• C. small size of $N_2$
• D. none of these

Answer 1

The correct option is B

extra stability of half filled ‘p’ orbital

Explanation for correct option:

(B) extra stability of half filled p orbital:

Ionization potential:

• Ionization energy is the amount of energy needed to remove an electron from an isolated atom.
• In a period, the ionization energy increases from left to right and decreases down the group.

Ionization energy of nitrogen is greater than oxygen:

• When an atom's valence orbital is completely or half-filled, it is very stable, and the valence p orbital in nitrogen is exactly half-filled.
• The valence p orbital in nitrogen $\left(2{\mathrm{p}}^3\right)$ is more stable than the valence p orbital in oxygen $\left(2{\mathrm{p}}^4\right)$, which contains one more electron than the half-filled configuration.
• As a result, nitrogen has higher ionization energy than oxygen.

Hence, (B) is the correct option.

Explanation for incorrect options:

(A) Higher ionization energy of nitrogen as compared to oxygen is not due to the increased attraction of electron towards the nucleus.

(C) Higher ionization energy of nitrogen as compared to oxygen is not due to the small size of ${\mathrm{N}}_2$.

Higher ionization energy is due to the extra stability of half filled p orbital. Therefore, all the other options (A), (C), and (D) are incorrect.

Therefore, the correct option is (B) extra stability of half filled p orbital.