Question

The color of $KMn{O}_4$ is due to :

• A. $M$ $\to$ $L$ charge transfer transition
• B. $L$ $\to$ $M$ charge transfer transition
• C. $\sigma -{\sigma }^{\ast }$ transition
• D. $d-d$ transition

Answer 1

Answer: (B)

The $Mn$ atom in $KMn{O}_4$ has $+7$ oxidation state with electron configuration $\left[Ar\right]3d^{0}4s^0$.
Since no unpaired electrons are present, $d-d$ transitions are not possible. The molecule should, therefore, be colourless.
The colour of $KMn{O}_4$ is intense purple due to $L\to M$ (ligand to metal) charge transfer 2p(L) of O to 3d(M) of Mn.