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JEE MAIN 2025
07.04.25 S2
Question
The number of paramagnetic metal complex species among $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+},\left[\mathrm{Co}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]^{3-}$, $\left[\mathrm{MnCl}_6\right]^{3-},\left[\mathrm{Mn}(\mathrm{CN})_6\right]^{3-},\left[\mathrm{CoF}_6\right]^{3-},\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{3-}$ and $\left[\mathrm{FeF}_6\right]^{3-}$ with same number of unpaired electrons is $\_\_\_\_$ ↓
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Solution
$\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} \mathrm{Co}^{3+} \quad 3 \mathrm{~d}^6 \quad \mathrm{t}_{2 \mathrm{~g}}^{2,2,2} \quad \mathrm{e}_{\mathrm{g}}^{0,0}$ Diamagnetic (unpaired electron $=0$ ) $\left[\mathrm{Co}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]^3 \mathrm{Co}^{3+} \quad 3 \mathrm{~d}^6 \quad \mathrm{t}_{2 \mathrm{~g}}^{2,2,2} \quad e_{\mathrm{g}}^{0,0}$ Diamagnetic (unpaired electron $=0$ ) $\left[\begin{array}{lllll}\mathrm{MnCl}_6 & ]^{3-} & \mathrm{Mn}^{3+} & 3 \mathrm{~d}^4 & \mathrm{t}_{2 \mathrm{~g}}^{1,1,1}\end{array} e_{\mathrm{g}}^{1.0}\right.$ Paramagnetic (unpaired electron $=4$ ) $\left[\begin{array}{lllll}\mathrm{Mn}(\mathrm{CN})_6 & ]^{3-} & \mathrm{Mn}^{3+} & 3 \mathrm{~d}^4 & \mathrm{t}_{2 \mathrm{~g}}^{2,1,1} \\ e_{\mathrm{g}}^{0,0}\end{array}\right.$ Paramagnetic (unpaired electron $=2$ ) $\left[\begin{array}{lllll}\mathrm{CoF}_6 & ]^{3-} & \mathrm{Co}^{3+} & 3 \mathrm{~d}^6 & \mathrm{t}_{2 \mathrm{~g}}^{2,1,1} \\ & e_{\mathrm{e}}^{1,1}\end{array}\right.$ Paramagnetic (unpaired electron $=4$ ) $\left[\begin{array}{lllll}\mathrm{Fe}(\mathrm{CN})_6 & ]^{3-} & \mathrm{Fe}^{3+} & 3 \mathrm{~d}^5 & \mathrm{t}_{2 \mathrm{~g}}^{2,2,1} \\ e_9^0\end{array}\right.$ Paramagnetic (unpaired electron $=1$ ) $\left[\begin{array}{lllll}\mathrm{FeF}_6 & ]^{3-} & \mathrm{Fe}^{3+} & 3 \mathrm{~d}^5 & \mathrm{t}_{2 \mathrm{~g}}^{1,1,1} \\ & \mathrm{e}_{\mathrm{e}}^{1,1}\end{array}\right.$ Paramagnetic (unpaired electron $=5$ )
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