$\mu=\sqrt{n(n+2)} B \cdot M$

$\mathrm{n}=$ no. of unpaired $e^-$

$\mu=1.73$

$1.73=\sqrt{n(n+2)} B \cdot M$

$n=1$

$\left[C o C l_{6}\right]^{4-} \rightarrow C o^{+2} ; d^{7}$

$\mathrm{Cl}^ -$ (weak field ligand) unpaired $e^{-}=3$

$\left[C u\left(N H_{3}\right)_{4}\right]^{2+} C u^{+2}-d^{9}$

$N H_{3}$ Strong field ligand, hybridisation $d s p^{2}$ one $e^{-}$ of $3 d$

$\left[N i(C N)_{4}\right]^{2-} \rightarrow N i^{+2}-d^{8}$ unpaired $e^{-}=0$

$C N^{-}$ - Strong field ligand $d s p^{2}$

$T i C l_{4} \rightarrow T i^{+4} d^{o}$ unpaired $e^-=z e r o$