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Question
Cuprous ion is colourless while cupric ion is coloured because ______.
Options
both have half filled p-and d-orbitals
cuprous ion has incomplete d-orbital and cupric ion has a complete d-orbital
both have unpaired electrons in the d-orbitals
cuprous ion has complete d-orbital and cupric ion has an incomplete d-orbital.
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Solution
Cuprous ion is colourless while cupric ion is coloured because cuprous ion has complete d-orbital and cupric ion has an incomplete d-orbital.
Explanation:
Cu+ has the configuration [Ar] 3d10 (filled d‑shell) so no low‑energy d → d transitions and it is usually colourless. Cu2+ is [Ar] 3d9 (partially filled d‑orbitals), allowing d–d electronic transitions (and often Jahn–Teller distortions) that absorb visible light and give coloured compounds.
