Q. Amongst ${TiF}_{6}^{2 -}$ , ${CoF}_{6}^{3 -}$, ${Cu}_{2}{Cl}_{2}$ and ${NiCl}_{4}^{2 -}$ (atomic no Ti=22, Co=27, Cu=29,Ni=28) the colourless species are
A) ${CoF}_{6}^{3 -}$and ${NiCl}_{4}^{2 -}$
B) ${TiF}_{6}^{2 -}$and ${CoF}_{6}^{3 -}$,
C) ${Cu}_{2}{Cl}_{2}$ and ${NiCl}_{4}^{2 -}$
D) ${TiF}_{6}^{2 -}$and ${Cu}_{2}{Cl}_{2}$
Explanation
(d)
Transitional metal ion having unpaired electrons are coloured while those which have no unpaired electron are colourless.
${TiF}_{6}^{2 -}$
${Ti}^{4 +}$ :[Ar]3$d^{0}$;0 unpaired electrons; colourless
${Cu}_{2}{Cl}_{2}$
${Cu}^{+}$:[Ar]3$d^{10}$;0 unpaired electrons; colourless
${CoF}_{6}^{3 -}$,
${CO}^{3 +}$:[Ar]$3d^{6}$;4 unpaired electrons; coloured
${NiCl}_{4}^{2 -}$
${Ni}^{2 +}$:[Ar]$3d^{8}$;2 unpaired electrons; coloured
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.