Question

Which of the following complex ion is not expected to absorb visible light?

• A. $\left[Ni\right(H_{2}O{)}_6{]}^{2+}$
• B. $\left[Ni\right(CN{)}_4{]}^{2-}$
• C. $\left[Cr\right(N{H}_3{)}_6{]}^{3+}$
• D. $\left[Fe\right(H_{2}O{)}_6{]}^{2+}$

Answer 1

The correct option is B

$\left[Ni\right(CN{)}_4{]}^{2-}$

In $\left[Ni\right(CN{)}_4{]}^{2-}$, the scenario is like $N{i}^{2+}\Rightarrow 3d^8$, pairing happens.
$\Rightarrow$

$\Rightarrow$ No possibility of transition

$\Rightarrow$Will not absorb visible light