Q3 · 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 $(\mathrm{Gd})$ is $\mathrm{[Xe]4f^{7}\,5d^{1}6s^{2}}$, where as that of $\mathrm{Gd^{2+}}$ is:
(a)$[\mathrm{Xe}] 4 \mathrm{f}^{5} 5 \mathrm{d} 6 \mathrm{s}^{2}$
(b)$[\mathrm{Xe}] 4 \mathrm{f}^{6} \mathrm{6s}^{2}$
(c)$[\mathrm{Xe}] \mathrm{f}^{6} 5 \mathrm{d}^{1} 6 \mathrm{s}^{1}$
(d)$[\mathrm{Xe}] 4 f^{7} 5 d^{1}$
Answer
Answer: D ✓ checked by 4AB · confidence high
Explanation
Gd is [Xe]4f⁷5d¹6s². Ionisation removes the outermost 6s electrons first, so Gd²⁺ is [Xe]4f⁷5d¹; the half-filled 4f⁷ shell is kept.
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