Among `[TiF_(6)]^(2-),[CoF_(6)]^(3-),Cu_(2)Cl_(2)` and `[NiCl_(4)]^(2-)` `["Atomic number" Ti=22,Co=27,Cu=29,Ni=28]` the Colourless species are:

Options

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

Answer

B

Explanation

The species with `3d^(0)` and `3d(10)` configuration are colourless . When it contains unpaired 3d electrons , it is capable of undergoing d-d transition by absorbing light of a particular wavelength from visible region of light and hence coloured.
In `TiF_(6)^(2-)` , `Ti^(4+)` , `3d^(0)` (colourless)
In `CoF_(6)^(3-)` , `Co^(3+)` , `3d^(6)` (colourled)
In `Cu_(2)Cl_(2)` , `Cu^(+)` , `3d^(10)` (colourless)
In `NICl_(4)^(2-)` , `Ni^(2+)` , `3d^(8)` (coloured)
Therefore , `TiF_(6)^(2-)` and `Cu_(2)Cl_(2)` are colourless.