Question

Amongst $TiC{l}_6^{2-},Co{F}_6^{3-},{Cu}_2{Cl}_2$ and $NiC{l}_4^{2-}$ the colourless species are:

• A. $Co{F}_6^{3-}$ and $NiC{l}_4^{2-}$
• B. $Ti{F}_6^{2-}$ and $Co{F}_6^{3-}$
• C. ${Cu}_2{Cl}_2$ and $NiC{l}_4^{2-}$
• D. $TiC{l}_6^{2-}$ and ${Cu}_2{Cl}_2$

Answer 1

The correct option is D $TiC{l}_6^{2-}$ and ${Cu}_2{Cl}_2$

In $TiC{l}_6^{2-}$, the $T{i}^{4+}$ ion has $3d^0$ electronic configuration. All electrons are paired.No d-d transition is possible. Hence, it is colourless.

In $Co{F}_6^{3-}$, the $C{o}^{3+}$ ion has $3d^6$ electronic configuration and contains 4 unpaired electrons.Hence, it is coloured.

In ${Cu}_2{Cl}_2$, the $C{u}^{+}$ ion has $3d^{10}$ electronic configuration and is colourless as all the electrons are paired.

In $NiC{l}_4^{2-}$, the $N{i}^{2+}$ ion has $3d^8$ electronic configuration. It contains 2 unpaired electrons and is coloured.

Hence, option $D$ is correct.