Which element from following forms colourless compounds in $+2$ oxidation state?

Which element from following forms colourless compounds in $+2$ oxidation state?
  1. $\operatorname{Co}(\mathrm{Z}=27)$
  2. $\operatorname{Zn}(\mathrm{Z}=30)$
  3. $\operatorname{Cu}(Z=29)$
  4. $\mathrm{Mn}(\mathrm{Z}=25)$

Solution

$\operatorname{Zn}(Z=30)$ $\mathrm{Zn}^{2+} \longrightarrow 3 \mathrm{~d}^{10}$ (No unpaired d-electron) $\therefore \mathrm{Zn}$ forms colourless compounds in $+2$ oxidation state.

Asked in: MHT CET 2020 (13 Oct Shift 1)

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