Aqueous solutions of Sc³⁺ salts are colourless because Sc³⁺ ____.
Correct answer A. has no 3d electrons available for d-d transitions
Explanation
Scandium is [Ar]3d¹4s², so Sc³⁺ is [Ar]3d⁰. With no d electrons, no d-d transitions can absorb visible light, so its compounds are colourless.
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