JEE Main · 2026 · 04 Apr 2026 · Shift 2 · d and f Block Elements

The highest oxide of manganese is $\mathrm{M}{\mathrm{n}}_2{\mathrm{O}}_7$, in which Mn is $+7$, and its highest fluoride is $\mathrm{Mn}{\mathrm{F}}_4$, in which Mn is $+4$ (fluorine cannot drive manganese as high as oxygen does), so $|x|=|7-4|=3$. The ions are now tested for three unpaired electrons: $\mathrm{S}{\mathrm{c}}^{3+}$ is $3d^0$ (0), $\mathrm{Z}{\mathrm{n}}^{2+}$ is $3d^{10}$ (0), ${\mathrm{V}}^{2+}$ is $3d^3$ (3), $\mathrm{F}{\mathrm{e}}^{2+}$ is $3d^6$ (4), and $\mathrm{C}{\mathrm{o}}^{2+}$ is $3d^7$ (3). The ions having three unpaired electrons are ${\mathrm{V}}^{2+}$ and $\mathrm{C}{\mathrm{o}}^{2+}$.