Question

Among $Ni\left(C{O}_4\right)$ , $Ni(CN{)}_4^{2-}$ and $Ni\left(C{l}_4^{2-}\right)$ :

• A. $Ni\left(C{O}_4\right)$ and $Ni\left(C{l}_4^{2-}\right)$ are diamagnetic and $Ni(CN{)}_4^{2-}$ is paramagnetic
• B. $Ni\left(C{l}_4^{2-}\right)$ and $Ni(CN{)}_4^{2-}$ are diamagnetic and $Ni\left(C{O}_4\right)$ is paramagnetic
• C. $Ni\left(C{O}_4\right)$ and $Ni(CN{)}_4^{2-}$ are diamagnetic and $Ni\left(C{l}_4^{2-}\right)$ is paramagnetic
• D. $Ni\left(C{O}_4\right)$ is diamagnetic and $Ni\left(C{l}_4^{2-}\right)$ and $Ni(CN{)}_4^{2-}$ are paramagnetic

Answer 1

Answer: (C)

$Ni\left(C{O}_4\right)$ and $Ni(CN{)}_4^{2-}$ are diamagnetic and $Ni\left(C{l}_4^{2-}\right)$ is paramagnetic

As CO and $C{N}^{-}$ are strong ligand they form low spin complex and pairing happens, therefore, they are diamagnetic but $C{l}^{-}$ is a weak ligand, it has higher spin outer orbital complex. In $Ni\left(C{l}_4^{2-}\right)$ complex Ni has 2 unpaired electron so it is paramagnetic.