Question

The complex having the highest magnetic moment is :

• A. $\left[Zn\right(H_{2}O{)}_6{]}^{2+}$
• B. $\left[Cr\right(H_{2}O{)}_6{]}^{2+}$
• C. $\left[Mn\right(H_{2}O{)}_6{]}^{2+}$
• D. $\left[Cu\right(H_{2}O{)}_6{]}^{2+}$

Answer 1

The correct option is C $\left[Mn\right(H_{2}O{)}_6{]}^{2+}$

The magnetic moment is given by $\sqrt{n(n+2)}$ Bohr magneton, where $n$ is the number of unpaired electrons.
As $H_{2}O$ is a weak ligand, it cannot force $3d$ electrons to pair.

Now, greater is the number of unpaired electrons, higher is the magnetic moment.
The electronic configurations of all the complexes is shown in the figure.

Therefore, it is clear that $\left[Mn\right(H_{2}O{)}_6{]}^{2+}$ has the maximum number of unpaired electrons and hence, the highest magnetic moment.