Question

Assertion (A): 16th group elements have higher ionization enthalpy values than 15th group elements in the corresponding periods.
Reason (R): 15th group elements have half-filled stable electronic configuration.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A).
• C. (A) is correct but (R) is incorrect.
• D. (A) is incorrect but (R) is correct.

Hint:

Half-filled subshells (e.g., \(np^3\)) are stable due to exchange energy, leading to higher ionization enthalpy for Group 15 elements compared to Group 16.

Answer 1

The Correct Option is D

Group 15 elements (e.g., N, P) have an outer configuration of \(ns^2np^3\), which is half-filled and stable, while Group 16 elements (e.g., O, S) have \(ns^2np^4\). The half-filled \(np^3\) configuration in Group 15 is more stable, leading to higher ionization enthalpy compared to Group 16 elements. For example, N (1402 kJ/mol) has a higher ionization enthalpy than O (1314 kJ/mol). Thus, the assertion (A) that Group 16 elements have higher ionization enthalpy is incorrect; the reverse is true. The reason (R) is correct, as Group 15 elements do have a half-filled stable configuration. However, (R) explains why Group 15 has higher ionization enthalpy, not Group 16, so it does not support (A). Therefore, (A) is incorrect, but (R) is correct. Thus, the correct answer is option 4.