Q58 / 180 · AIIMS 2019 (25 May) · Chemistry

Assertion : $\mathrm{Yb}^{2+}$ is more stable as compare to $\mathrm{Gd}^{2+}$. Reason : The electronic configuration of Gd is [ $\mathrm{Xe}] 4 f^7 5 d^2 6 s^2$.

  • A
    If both assertion and reason are true and reason is the correct explanation of assertion.
  • B
    If both assertion and reason are true but reason is not the correct explanation of assertion.
  • Correct answer
    C
    If assertion is true but reason is false.
  • D
    If both assertion and reason are false.

Solution

$\begin{aligned} & \text { } \mathrm{Yb}^{2+}=[\mathrm{Xe}] 4 f^{14} 5 d^0 6 s^0 \\ & \mathrm{Gd}^{2+}=[\mathrm{Xe}] 4 f^7 5 d^1 6 s^0\end{aligned}$ Because of fully filled $4 f$ orbital, $\mathrm{Yb}^{2+}$ is more stable than $\mathrm{Gd}^{2+}$.

Hence, the correct answer is option: 'C'.

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