The color of `KMnO_(4)` is due to

Options

A. d-d transition
B. L `rarr` M charge transfer transition
C. `sigma - sigma^(**)` transition
D. M `rarr` L charge transfer transition

Answer

B

Explanation

The permanganate ion has an intense purple colour. The oxidation state of Mn in `KMnO_(4)` is `(+7)`. Ground state configuration of Mn is `3d^(6) 4s^(2)` . Thus, Mn `(+7)` has a `d^(0)` configuration. The color arises form charge transfer and not for d-d transition. In `MnO_(4)^(-)`, an electron is momentarily transferred form O(L) to the metal (M), thus momentarily changing `O^(2-)` to `O^(-)` and reducing the oxidation state of the metal from `Mn(+7)` to Mn `(+6)`.