Q155 · CSIR NET Chemistry, June 2011
Paper: CSIR NET June 2011 · Subject: Inorganic Chemistry · Chapter: Lanthanides and Actinides · Topic: Lanthanides & Actinides – General · Marks: 2 · Difficulty: Medium
The electronic configuration for gadalonium (Gd) is $[\mathrm{Xe}]4\mathrm{f}^{7} 5\mathrm{d}^{1} 6\mathrm{s}^{2}$, where as that of $\mathrm{Gd}^{2+}$ is:
(a)$[\mathrm{Xe}]4\mathrm{f}^{5} 5\mathrm{d}\ 6\mathrm{s}^{2}$
(b)$[\mathrm{Xe}] 4 \mathrm{f}^{6} 6 \mathrm{s}^{2}$
(c)$[\mathrm{Xe}]\mathrm{f}^{6} 5\mathrm{d}^{1} 6\mathrm{s}^{1}$
(d)$[\mathrm{Xe}] 4 \mathrm{f}^{7} 5 \mathrm{d}^{1}$
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
Ionisation removes the 6s electrons first: Gd²⁺ is [Xe]4f⁷5d¹, keeping the stable half-filled f shell.
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