(2)

:

Ni is zero-valent with configuration .
CO is a strong field ligand causing complete pairing in the filled orbital.
Unpaired electrons .
:
Ni is +2 with configuration .
Cl is a weak field ligand producing high-spin tetrahedral geometry with configuration : five orbitals with two electrons paired, three electrons unpaired.
Unpaired electrons .
:
Pt is +2 with configuration .
adopts square planar geometry with strong-field splitting leading to complete pairing: configuration places all electrons in bonding orbitals.
Unpaired electrons .
:
Ni is +2 with configuration.
CN is a strong field ligand.
Square planar geometry is preferred, resulting in all electrons paired.
Unpaired electrons .
:
Pt is +2 with configuration.
CN is a strong field ligand producing square planar geometry with complete pairing.
Unpaired electrons .

Total unpaired electrons .