With the help of Valence Bond theory account for hybridisation, geometry and magnetic property of `[Ni(CN)_(4)]^(2-)` complex ion `[Z" for "Ni=28]`

Explanation

In this complex, the oxidation state of nickel is `+2` and has an electronic configuration of `[Ar]3d^8`.
`Ni^(2+) : [Ar]3d^8`.

ln this case, the two unpaired electrons of the 3d - orbitals are forced to pair in the presence of a strong ligand `CN^(-)` ion. Since four ligands are to be accomodated, nickel (II) ion undergoes `dsp^2` hybridisation forming four equivalent `dsp^2` hybrid orbitals.

These four hybrid orbitals overlap with the orbitals of lignads and ligands donate four pairs of electrons to form four coordinate bonds.

Since the complex undergoes `dsp^2` hybridization, the geometry is squire planar. It is diamagnetic complex due to the absence of unpaired electrons. During the formation of the complex, since the inner 3d-orbitals is used in the hybridisation `[Ni(CN)_4]^(2-)` is called inner orbital complex or spin paired complex or low spin on hyper ligand complex.