Question

Assertion :$\left[Ni\right(CN{)}_4{]}^{-2}$ has zero unpaired electron while that of $[NiC{l}_4{]}^{-2}$ has two unpaired $e^{-}$ Reason: $[NiC{N}_4{]}^{-2}$ has strong crystal field while $[NiC{l}_4{]}^{-2}$ has weak crystal field

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Option (A) is correct.
$\left[Ni\right(CN{)}_4{]}^{-2}$ has zero unpaired electron while that of $[NiC{l}_4{]}^{-2}$ has two unpaired $e^{-}$ In both cases, $Ni$ has $d^8$ orbitals but in case of $[NiC{N}_4{]}^{-2}$, $CN$ being a strong ligand so all the electrons are paired up and has no unpaired electrons but in case of $[NiC{l}_4{]}^{-2}$, $Cl$ being a weak ligand so there are 2 unpaired electrons.
Hence $[NiC{N}_4{]}^{-2}$ has strong crystal field while $[NiC{l}_4{]}^{-2}$ has weak crystal field.