JEE Main 2018 — Coordination Compounds Question with Solution

${\left[{\mathrm{NiCl}}_4\right]}^{-2}$  
Tetrahedral 
Paramagnetic 

$\left[\mathrm{Ni}{\left(\mathrm{CO}\right)}_4\right]$
Tetrahedral 
Diamagnetic 

Weak field ligand (WFL)
Strong field ligand(SFL)

${\left[{\mathrm{NiCl}}_4\right]}^{2-}$	$\left[\mathrm{Ni}{\left(\mathrm{CO}\right)}_4\right]$
Paramagnetic ($2$ unpaired electrons)	${\mathrm{Sp}}^3$
${\mathrm{Ni}}^{2+}\to \left[\mathrm{Ar}\right]\mathrm{ }3{\mathrm{d}}^8,\mathrm{ }4{\mathrm{s}}^0,\mathrm{ }4{\mathrm{p}}^0$
${\mathrm{Cl}}^{-}$ (WFL) (No pairing)	$\mathrm{Ni}\left(\mathrm{O}\right)\to \left[\mathrm{Ar}\right]3{\mathrm{d}}^8,\mathrm{ }4{\mathrm{s}}^2,\mathrm{ }4{\mathrm{p}}^0$
	$\mathrm{CO}$ is SFL $\left[\mathrm{Ar}\right]3{\mathrm{d}}^{10},\mathrm{ }4{\mathrm{s}}^0,\mathrm{ }4{\mathrm{p}}^0$ (tetrahedral)