alleryWhich of the following ions is colourless and diamagnetic?
ASc³⁺ (3d⁰) and Zn²⁺ (3d¹⁰)
BFe³⁺ (3d⁵)
CMn²⁺ (3d⁵)
DCu²⁺ (3d⁹)
Answer & Solution
Correct answer: A. Sc³⁺ (3d⁰) and Zn²⁺ (3d¹⁰)
**Colourless + diamagnetic** requires **no unpaired d-electrons AND no possible d-d transition**: **d⁰ (Sc³⁺, Ti⁴⁺)** and **d¹⁰ (Zn²⁺, Cu⁺)** ions.
All others with d¹–d⁹ are coloured (d-d transitions) and paramagnetic.
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