${\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]}^{3-}$ has ${\mathrm{Fe}}^{3+}$ central ion $\left({\mathrm{d}}^5\right)$

Electronic configuration (SFL)

${\mathrm{t}}_{2\mathrm{g}}{{}^{2,2,1}\mathrm{e}_{\mathrm{g}}}^{0,0}$

$\mathrm{n}=1$

Magnetic moment:

$\mathrm{\mu }=\sqrt{\mathrm{n}\left(\mathrm{n}+2\right)} \mathrm{BM}$

$=\sqrt{1(1+2)}$

$=\sqrt{3}$

$=1.73 \mathrm{BM}$

${\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}:$ has ${\mathrm{d}}^5$ electrons.

Electronic configuration (WFL)

${\mathrm{t}}_{2\mathrm{g}}{{}^{1,1,1}\mathrm{e}}_{\mathrm{g}}^{1,1}$

$\mathrm{n}=5$

$\mathrm{\mu }=\sqrt{5(5+2)}=\sqrt{35}$

$=5.92 \mathrm{B}.\mathrm{M}.$

${\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]}^{4-}$ has ${\mathrm{d}}^6$ electrons.
Electronic configuration (SFL)

${\mathrm{t}}_{2\mathrm{g}}^{2,2,1}{\mathrm{e}}_{\mathrm{g}}^{0,0}$

$\mathrm{n}=0$

$\mathrm{\mu }=0 \mathrm{B}.\mathrm{M}.$

${\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ has ${\mathrm{d}}^6$ electron
Electronic configuration: (WFL)

${\mathrm{t}}_{2\mathrm{g}}^{2,2,1}{\mathrm{e}}_{\mathrm{g}}^{1,1}$

$\mathrm{n}=4$

$\mathrm{\mu }=\sqrt{4(4+2)}=4.90 \mathrm{B}.\mathrm{M}.$