Which one of the following forms a colourless solution in aqueous medium ?
(Atomic number : `Sc =21, Ti = 22, V = 23`, and `Cr = 24`)

Options

A. `V^(3+)`
B. `Cr^(3+)`
C. `Ti^(3+)`
D. `Sc^(3+)`

Answer

D

Explanation

Colour is usually due to d-d trnsition :
`V (3d^(3) 4s^(2)) implies V^(3+) (3d^(2))` : coloured
`Cr (3d^(5) 4s^(1)) implies Cr^(3+) (3d^(3))` : colored
`Ti (3d^(2) 4s^(2)) implies Ti^(3+) (3d^(1))` : coloured
`Sc (3d^(1) 4s^(2)) implies Sc^(3+) (3d^(0))` : colourless.