Question
Chemistry Question on The Lanthanoids
The purple colour of KMnO4 is due to the transition
A
C.T.(L→M)
B
C.T.(M→L)
C
d−d
D
p−d
Answer
C.T.(L→M)
Explanation
Solution
The permanganate ion has an intense purple colour. Mn (+ VII) has a d0 configuration. So the colour arises from charge transfer and not from d?d spectra.
In MnO4− an electron is momentarily changing O−− to O− and reducing the oxidation state of the metal from Mn(VII) to Mn (VI). Charge transfer requires that the energy levels on the two different atoms are fairly close.
O=(8)=2K,6L
Mn(25)=2K,8L,15M
hence the charge transfer occurs from L→M