Amongst `[TiE_(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) `[TiF_(6)]^(2-)` and `[Cu_(2)Cl_(2)]`
(B) `Cu_(2)Cl_(2)` and `[NiCl_(4)]^(2-)`
(C) `[TiF_(6)]^(2-)` and `[CoF_(6)]^(3-)`
(D) `[CoF_(6)]^(3-)` and `[NiCl_(4)]^(2-)`

Options

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)`

Answer

D

Explanation

Transition metal ions having unpaired electrons are coloured while those which those which have no unpaired electron are colourless
In `TiF_(6)^(2-),Ti^(4+):[Ar]3d^(0),0` unpaired electron, colourless
In `Cu_(2)Cl_(2),Cu^(+):[Ar]3d^(10),0` unpaired electrons, colourless
In`COf_(6)^(3-),CO^(3+):[Ar]3d^(6),4`
In` NiCl_(4)^(2-), Ni^(2+):[Ar]3d^(8),2` unpaired electrons, coloured