Cuprous ion is colourless while cupric ion is coloured because

Cuprous ion is colourless while cupric ion is coloured because
  1. both have half filled $p$ -and $d$ -orbitals.
  2. cuprous ion has incomplete $d$ -orbital and cupric ion has a complete $d$ -orbital.
  3. both have unpaired electrons in the $d$ -orbitals.
  4. cuprous ion has complete $d$ -orbital and cupric ion has an incomplete $d$ -orbital.

Solution

(d) In $\mathrm{Cu}^{+}[\mathrm{Ar}] 3 \mathrm{~d}^{10}$ there is no unpaired electron, $\mathrm{Cu}^{2+}[\mathrm{Ar}] 3 \mathrm{~d}^{9}$ contains one unpaired
electron hence coloured.

Asked in: JEE-TOPICTESTS-CHEMISTRY

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