Predict which of the following will be coloured in aqueous solution? `Ti^(3+),V^(3+), Cu^(+),Sc^(3+),Mn^(2+),Fe^(3+)` and `Co^(2+)`. Give reasons for each.

Options

A. `Ti^(3+), V^(3+)`
B. `Cu^(+), Sc^(3+)`
C. `Cu^(2+), Fe^(2+)`
D. `Co^(2+), Ni^(2+)`

Answer

B

Explanation

Only those ions will be coloured which have incompletely filled d-orbitals.Those with fully-filled or empty d-orbitals are mostly colourless. Thus, `Ti^(3+)(3d^1),V^(3+)(3d^2),Cr^(3+)(3d^3),Cu^(2+)(3d^9), Fe^(3+)(3d^5) and Co^(2+)(3d^7)` are all coloured due to d-d transition. Only `Sc^(3+)(3d^0)` is colourless.