Which one of the following ionic species will impart colour to an aqueous solution ?

Options

A. `Ti^(4+)`
B. `Cu^(+)`
C. `Zn^(2+)`
D. `Cr^(3+)`

Answer

D

Explanation

`Cr^(3+) = 1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)3d^(3)` (coloured)
`(Cr^(3+)` contains 3 unpaired `e^(-)`, so it gives colour)
`Zn^(2+)=1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)3d^(10)` (colourless)
`Cu^(+) = 1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)3d^(10)` (colourless)
`Ti^(4+) = 1s^(2), 2s^(2)2p^(6),3s^(2)3p^(6)` (colourless)
(Colour is produced due to presence of unpaired electrons).