The observed magnetic moment of the complex [ Mn ( NCS ) _ 6 ) ] ^...

The complex $[ Mn ( NCS{)}_{6} ) {]}^{x -}$ has a magnetic moment of$6 . 06BM$. This indicates that the complex has unpaired electrons, which contribute to its magnetic moment.

Number of unpaired electrons $= 5$$( {Mn}^{2 +}: 3{d}^{5} )$.
So $Mn$ must be in $+ 2$ oxidation state ${Mn}^{2 +}$.

$⇒ 2 + ( – 6 ) = – x ⇒ – 4 = – x ⇒ x = 4$
The numerical value of $x$ is $4$, so the complex is $[ Mn ( NCS{)}_{6} ) {]}^{4 -}$.