Amongst the following ions which one has the highest magnetic moment value?

(i) No. of unpaired electrons in $\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}=3$

Then, $\mu=\sqrt{n(n+2)}$

$=\sqrt{3(3+2)}$

$=\sqrt{15}$

$\sim 4 \mathrm{BM}$

(ii) No. of unpaired electrons in [Fe(H2O)6]2+ = 4

Then, $\mu=\sqrt{4(4+2)}$

$=\sqrt{24}$

$\sim 5 \mathrm{BM}$

(iii) No. of unpaired electrons in [Zn(H2O)6]2+ = 0

Hence, [Fe(H2O)6]2+ has the highest magnetic moment value.