Question

Among the following ions which one has the highest paramagnetism?

• A. $\left[Cr\right(H_{2}O{)}_6{]}^{3+}$
• B. $\left[Fe\right(H_{2}O{)}_6{]}^{2+}$
• C. $\left[Cu\right(H_{2}O{)}_6{]}^{2+}$
• D. $\left[Zn\right(H_{2}O{)}_6{]}^{2+}$

Answer 1

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

The electronic configuration of metal ions is not much affected by weak field ligand water. Hence, the electronic configurations of metal ions coordinated to water are same as in isolated ions.
The outer shell electronic configurations of metal ions in above complexes are shown below.



$F{e}^{2+}$ ion has more number of unpaired electrons. Hence, $\left[Fe\right(H_{2}O{)}_6{]}^{2+}$ is more paramagnetic.
Note: The charge on metal ions is equal to the charge on the complex since water is a neutral ligand.