AIIMS 2019 Chemistry Lanthanides Assertion Reason Question
The electron configuration of Yb⁺² is [Xe]₄f¹⁴5d⁰6s⁰ and the electron configuration of Gd⁺² is [Xe]₄f⁷5d¹6s⁰ So, Yb⁺² is more stable in compare to Gd⁺² due to the fully filled stabilized electron configuration. So, the assertion is true but the reason is false.
Both assertion and reason are true and reason is the correct explanation of assertion.
Both assertion and reason are true but reason is not the correct explanation of assertion.
Assertion is true but reason is false.
Both assertion and reason are false.
Correct Answer
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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