Coordination Compounds

The complex ion $[\mathrm{Mn}(\mathrm{Cl})_6]^{3-}$ has a spin-only magnetic moment of 4.90 B.M.Oxidation State and Electron Configuration:For Mn in this ion, the oxidation state is +3 . This means manganese has lost three electrons.The electron configuration for $\mathrm{Mn}^{3+}$ is $[\mathrm{Ar}]\,3d^{4}$. This tells us the ion has 4 electrons in the 3 d orbitals.Finding the Magnetic Moment:The formula for the spin-only magnetic moment is:$\mu = \sqrt{n(n+2)} \; \text{ В.М. } \;$Here, $n$ is the number of unpaired electrons. For $\mathrm{Mn}^{3+}, n=4$ because there are 4 unpaired electrons in the $3d$ orbitals.Plug in the value of $n$ :$\mu = \sqrt{4(4+2)} = \sqrt{24} = 4.90 \; \text{ В.М. } \;$