Which of the following pairs of ions are colourless?

Options

A. `Ti^3+` ,`Cu^2+`
B. `Se^3+` , `Zn^2+`
C. `CO^2+` , `Fe^3+`
D. `Ni^2+` , `V^3+`

Answer

(b)

Explanation

d- block element form coloured ions due to presence of unpaired electrns in them . Since there are no presence of unpaired electrons in them . Since there are no unpaired electrons in `Se^3+` and `Zn^2+` ions , they are colourless .
no of unpaired s(n) `Ti^3+-[Ar]3d^1, Cu^2+ - [Ar] 3d^9` 1,1
`(Sc^2+ - [Ar] 3d^circ , Zn^2+ )- [Ar]3d(610) 0.0`
`(Co^2+ - [Ar] 3d^7)(Fe3+ -[Ar]3d)[Ar]^3d^5 3, 5`
`- ([Ar]3d^8 V^3+)- ([Ar]3d^2)` 2,2