For the complex${\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ write the electronic configuration of iron ion and predict its magnetic behaviour:

In $\left[\mathrm{Fe}\right(\mathrm{H}2\mathrm{O}\left)6\right]2+$, the oxidation state of Fe is + 2.
Electronic configuration of Fe (26) is ${\mathrm{d}}^{6}4{\mathrm{s}}^2$.
${\mathrm{Fe}}^{2+}=3{\mathrm{d}}^{6}4{\mathrm{s}}^0$
Or ${\mathrm{Fe}}^{2+}={\mathrm{t}}_{2\mathrm{g}}^4{\mathrm{e}}_{\mathrm{g}}^2$
The numbers of unpaired electrons are four.
Hence, it is paramagnetic.