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AIIMS2019Chemistry-Electronic Configuration

AIIMS 2019 Chemistry Lanthanides Assertion Reason Question

Type: Assertion Reason-conceptual-Medium

Assertion : Yb+2\text{Yb}^{+2} is more stable in compare to Gd+2\text{Gd}^{+2}

Reason : The electronic configuration of Gdis [Xe]4f75d26s2[\text{Xe}]4\text{f}^7 5\text{d}^2 6\text{s}^2.

A

Both assertion and reason are true and reason is the correct explanation of assertion.

B

Both assertion and reason are true but reason is not the correct explanation of assertion.

C

Assertion is true but reason is false.

D

Both assertion and reason are false.

Correct Answer

Option B

Detailed Explanation

Option B is correct because the assertion that Yb²⁺ is more stable than Gd²⁺ due to its fully filled electron configuration is true; fully filled subshells (like 4f¹⁴) confer greater stability. However, the reason provided is false because the stability of Yb²⁺ is not solely due to the filled 4f subshell, but rather the overall electron configuration and energy levels involved. Option A is incorrect as the reason does not correctly explain the assertion, while options C and D are incorrect because they misrepresent the truth of the assertion and reason.

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