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. `TiF_(6)^(2-)and CoF_(6)^(3-)`
B. `Cu_(2)Cl_(2) and NiCl_(4)^(2-)`
C. `TiF_(6)^(2-)and Cu_(2)Cl_(2)`
D. `CoF_(6)^(3-) and NiCl_(4)^(2-)`

Answer

C

Explanation

In `TiF_(6)^(2-),Ti" is present as "Ti^(4+).Ti^(4+)=[Ar] 3d^(0) 4s^(0)` Hence, `TiF_(6)^(2-)` is colourless due to the absence of unpaired electron.
In `Cu_(2)Cl_(2),Cu" is present as "Cu^(+).`

Due to absence of unpaired electrons, `Cu_(2)Cl_(2)` is colourless.