Chemistry - Coordination Chemistry Question with Solution | TestHub

In $\left[\mathrm{Ni}(\mathrm{CO}{)}_4\right]$, the oxidation state of $\mathrm{Ni}$ is zero $(0)$. $$\mathrm{Ni}(28)[\mathrm{Ar}]4{\mathrm{s}}^2,3d^8$$
$$\mathrm{CO}\text{ is a strong ligand, causes coupling, thus }$$
In ${\left[\mathrm{Ni}(\mathrm{CN}{)}_4\right]}^{2-}$, the oxidation state of $\mathrm{Ni}$ is $+2$ ${\mathrm{Ni}}^{2+}=[\mathrm{Ar}]3d^8,4s^0$
$${\mathrm{CN}}^{-}\text{is strong ligand causes coupling. }$$