JEE Main · 2025 · 23 Jan 2025 · Shift 1 · d and f Block Elements

Colour in a transition-metal ion arises from d–d transitions, which require a partially filled d subshell.

${\mathrm{V}}^{2+}$ ($3d^3$), $\mathrm{C}{\mathrm{r}}^{3+}$ ($3d^3$) and $\mathrm{M}{\mathrm{n}}^{3+}$ ($3d^4$) each retain unpaired d-electrons, and all three are observed as violet in aqueous solution.

The remaining sets each mix a colourless $d^0$ or $d^{10}$ ion ($\mathrm{Z}{\mathrm{n}}^{2+}$, $\mathrm{T}{\mathrm{i}}^{4+}$, $\mathrm{S}{\mathrm{c}}^{3+}$) with differently coloured ions, so no common colour is shared.

${\mathrm{V}}^{2+}$, $\mathrm{C}{\mathrm{r}}^{3+}$ and $\mathrm{M}{\mathrm{n}}^{3+}$ form the set sharing the same colour.