Consider the following complex ions
$\begin{array}{rl} & \mathrm{P}={\left[{\mathrm{FeF}}_6\right]}^{3-}\\ & \mathrm{Q}={\left[\mathrm{V}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}\\ & \mathrm{R}={\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}\end{array}$
The correct order of the complex ions, according to their spin only magnetic moment values (in B.M.) is :

${\left[{\mathrm{FeF}}_6\right]}^{3-}:{\mathrm{Fe}}^{+3}:\left[\mathrm{Ar}\right]3{\mathrm{d}}^5$
F : Weak field Ligand
No. of unpaired electron's = 5 
$\begin{array}{rl} & \mu =\sqrt{5(5+2)}\\ & \mu =\sqrt{35}\mathrm{BM}\\ & {\left[\mathrm{V}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{+2}:{\mathrm{V}}^{+2}:3{\mathrm{d}}^3\end{array}$

No. of unpaired electron's = 3
$\begin{array}{rl} & \mu =\sqrt{3(3+2)}\\ & \mu =\sqrt{15}\mathrm{BM}\\ & {\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{+2}:{\mathrm{Fe}}^{+2}:3{\mathrm{d}}^6\end{array}$
${\mathrm{H}}_2\mathrm{O}:$Weak field Ligand

No. of unpaired electron's = 4
$\begin{array}{rl} & \mu =\sqrt{4(4+2)}\\ & \mu =\sqrt{24}\mathrm{BM}\end{array}$