Out of KMnO4 and K2MnO4, KMnO4 is paramagnetic, while K2MnO4 is diamagnetic.
The paramagnetism of KMnO4 arises from the presence of unpaired electrons in the manganese (Mn) ion. In KMnO4, the oxidation state of manganese is +7, which is the highest oxidation state exhibited by manganese in its compounds. The electronic configuration of Mn in KMnO4 can be represented as follows:
Mn: [Ar] 3d^3 4s^2 4p^6 4d^3
In KMnO4, the Mn(VII) ion has three unpaired electrons in its 3d orbitals. These unpaired electrons give rise to paramagnetic behavior, as they align themselves with an external magnetic field, resulting in a net magnetic moment.
On the other hand, in K2MnO4, manganese is in the +6 oxidation state. The electronic configuration of the Mn ion in K2MnO4 can be represented as:
Mn: [Ar] 3d^3 4s^2 4p^6 4d^2
In K2MnO4, the Mn(VI) ion has only two unpaired electrons in its 3d orbitals. However, due to the presence of the MnO4^2- ion, which is highly symmetrical and involves d-orbitals in bonding, the net magnetic moment is canceled out, resulting in diamagnetic behavior.
In summary, KMnO4 is paramagnetic due to the presence of unpaired electrons in the Mn(VII) ion, while K2MnO4 is diamagnetic due to the cancellation of the net magnetic moment by the highly symmetrical structure of the Mn(VI) ion in the MnO4^2- ion.
