Question

The aqueous solution containing which one of the following ions will be colourless
(Atomic number `Sc = 21, Fe = 26, Ri = 22, Mn = 25)`
A. `Sc^(3+)`
B. `Fe^(2+)`
C. `Ti^(3+)`
D. `Mn^(2+)`

Answer 1

Correct Answer - A
Ions having (n - 1) `d^(0)` or (n - 1) `d^(10)` configuration are colourless on account of absence of d-d transition.
`Sc (3d^(1) 4s^(2)) implies Sc^(3+) (3d^(0)) implies` colourless
`Fe (3d^(6) 4s^(2)) implies Fe^(2+) (3d^(6)) implies` coloured
`Ti(3d^(2) 4s^(2)) implies Ti^(3+) (3d^(1)) implies` coloured
`Mn (3d^(5) 4s^(2)) implies Mn^(2+) (3d^(5)) implies` coloured