Explanation

(d)
For $\left\lbrack Ni(CN)_{4} \right\rbrack^{2 -}$, oxidation state of Ni is +2.
$CN^{-}$=strong field ligand
$Ni^{2 +}$(ground state)=
$3d^{8}$ $4s^{0}$
[table] ⥮ | ⥮ | ⥮ | $\upharpoonleft$ | $\upharpoonleft$ | | [/table]
In $\left\lbrack Ni(CN)_{4} \right\rbrack^{2 -}$
$Ni^{2 +} =$[image:9_image263.emf]
$dsp^{2}$ hybridisation, i.e., square planar geometry, zero unpaired electron, i.e., zero magnetic moment
For $\left\lbrack MnBr_{4} \right\rbrack^{2 -}$, oxidation state of Mn is +2.
$Br^{-}$= weak field ligand
$Mn^{2 +}$ (in ground state)
$3d$ $4s$
[table] $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | | | | | | [/table]
In $\left\lbrack MnBr_{4} \right\rbrack^{2 -}$,
$Mn^{2 +} =$ [image:9_image264.emf]
$sp^{3}$ hybrisation, i.e., tetrahedral geometry, five unpaired electrons, i.e., magnetic moment=5.9
$Co^{3 +}$ in ground state=
$3d$ $\ \ 4s^{0}$ $4p$
[table] ⥮ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | $\upharpoonleft$ | | | | | | [/table]
For $\left\lbrack CoF_{6} \right\rbrack^{3 -}$, oxidation state of Co is +3.
$F^{-}$=weak field ligand
$In\ \left\lbrack CoF_{6} \right\rbrack^{3 -}$
[image:9_image265.emf]
$sp^{3}\ d^{2}$ hybridisation i.e., octahedral geometry four unpaired electrons i.e., magnetic moment is 4.91 BM.