JEE Advanced 2025 Paper 1 Q06 Chemistry Inorganic Chemistry Periodic Table & Periodicity Medium

JEE Advanced 2025 Paper 1 · Q06 · Periodic Table & Periodicity

The pair(s) of diamagnetic ions is(are):

  1. A. $La^{3+}, Ce^{4+}$
  2. B. $Yb^{2+}, Lu^{3+}$
  3. C. $La^{2+}, Ce^{3+}$
  4. D. $Yb^{3+}, Lu^{2+}$
JEE Advanced multi-correct — pick every correct option, then check.
Reveal answer + step-by-step solution

Correct answer:A, B

Solution

Diamagnetic = no unpaired electrons. $La$ ($Z=57$): $[Xe] 5d^1 6s^2$ ⟹ $La^{3+} = [Xe]$, no unpaired $e^-$. $Ce$ ($Z=58$): $[Xe] 4f^1 5d^1 6s^2$ ⟹ $Ce^{4+} = [Xe]$, no unpaired. (A) both diamagnetic. TRUE. $Yb$ ($Z=70$): $[Xe] 4f^{14} 6s^2$ ⟹ $Yb^{2+} = [Xe] 4f^{14}$, all paired ⟹ diamagnetic. $Lu$ ($Z=71$): $[Xe] 4f^{14} 5d^1 6s^2$ ⟹ $Lu^{3+} = [Xe] 4f^{14}$, paired ⟹ diamagnetic. (B) both diamagnetic. TRUE. (C) $La^{2+}$: $[Xe] 5d^1$ (one unpaired $e^-$) — paramagnetic. So (C) FALSE. (D) $Yb^{3+}$: $[Xe] 4f^{13}$ (one unpaired) ⟹ paramagnetic; $Lu^{2+}$ would be $[Xe] 4f^{14} 5d^1$ ⟹ paramagnetic. (D) FALSE. Answer: A, B.

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