Question:
Assertion (A): \(16^{th}\) group elements have higher ionization enthalpy values than \(15^{th}\) group elements in the corresponding periods.
Reason (R): \(15^{th}\) group elements have half-filled stable electronic configurations.
Assertion (A): \(16^{th}\) group elements have higher ionization enthalpy values than \(15^{th}\) group elements in the corresponding periods.
Reason (R): \(15^{th}\) group elements have half-filled stable electronic configurations.
Reason (R): \(15^{th}\) group elements have half-filled stable electronic configurations.
Show Hint
Half-filled and completely filled electronic configurations are extra stable. Hence, group \(15\) elements generally have slightly higher ionization enthalpy than group \(16\) elements.
Updated On: Jun 22, 2026
- Both (A) and (R) are correct and (R) is the correct explanation of (A).
- Both (A) and (R) are correct but (R) is not the correct explanation of (A).
- (A) is correct but (R) is incorrect.
- (A) is incorrect but (R) is correct.
Show Solution
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The Correct Option is D
Solution and Explanation
Step 1: Analyze the assertion (A).
Generally, ionization enthalpy increases across a period from left to right due to increasing effective nuclear charge.
However, there is an exception between group \(15\) and group \(16\).
Elements of group \(15\) possess stable half-filled \(p\)-orbitals: \[ ns^2np^3 \] whereas group \(16\) elements have configuration: \[ ns^2np^4 \] In group \(16\), one \(p\)-orbital contains paired electrons, resulting in extra electron-electron repulsion.
Therefore, it becomes easier to remove one electron from group \(16\) elements.
Hence, \[ IE_{15}\gt IE_{16} \] Thus, the assertion stating that group \(16\) elements have higher ionization enthalpy than group \(15\) elements is incorrect.
Step 2: Analyze the reason (R).
Group \(15\) elements have electronic configuration: \[ ns^2np^3 \] This is a half-filled configuration which is especially stable due to symmetrical electron distribution and exchange energy.
Therefore, the reason is correct.
Step 3: Final conclusion.
Thus, \[ \boxed{\text{(A) is incorrect but (R) is correct}} \]
Generally, ionization enthalpy increases across a period from left to right due to increasing effective nuclear charge.
However, there is an exception between group \(15\) and group \(16\).
Elements of group \(15\) possess stable half-filled \(p\)-orbitals: \[ ns^2np^3 \] whereas group \(16\) elements have configuration: \[ ns^2np^4 \] In group \(16\), one \(p\)-orbital contains paired electrons, resulting in extra electron-electron repulsion.
Therefore, it becomes easier to remove one electron from group \(16\) elements.
Hence, \[ IE_{15}\gt IE_{16} \] Thus, the assertion stating that group \(16\) elements have higher ionization enthalpy than group \(15\) elements is incorrect.
Step 2: Analyze the reason (R).
Group \(15\) elements have electronic configuration: \[ ns^2np^3 \] This is a half-filled configuration which is especially stable due to symmetrical electron distribution and exchange energy.
Therefore, the reason is correct.
Step 3: Final conclusion.
Thus, \[ \boxed{\text{(A) is incorrect but (R) is correct}} \]
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