JEE MAIN - Chemistry (2022 - 29th July Morning Shift - No. 6)
In following pairs, the one in which both transition metal ions are colourless is :
$$\mathrm{Sc}^{3+}, \mathrm{Zn}^{2+}$$
$$\mathrm{Ti}^{4+}, \mathrm{Cu}^{2+}$$
$$\mathrm{V}^{2+}, \mathrm{Ti}^{3+}$$
$$\mathrm{Zn}^{2+}, \mathrm{Mn}^{2+}$$
Explanation
$\mathrm{Sc}^{+3}$ and $\mathrm{Zn}^{+2}$ are colourless as they contain no unpaired electron. Whereas the transition metal ions $\mathrm{Cu}^{+2}, \mathrm{Ti}^{+3}, \mathrm{~V}^{+2}$ and $\mathrm{Mn}^{+2}$ are coloured as they contain unpaired electrons.
The unpaired electron from lower energy $d$ orbital gets excited to a higher energy $d$ orbital on absorbing light of frequency which lies in visible region. The colour complementary to light absorbed is observed.
The unpaired electron from lower energy $d$ orbital gets excited to a higher energy $d$ orbital on absorbing light of frequency which lies in visible region. The colour complementary to light absorbed is observed.
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