The magnetic behaviour of manganate ion and permanganate ions, respectively, are
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → paramagnetic and diamagnetic
A substance is paramagnetic if it has one or more unpaired electrons (it is attracted by a magnetic field) and diamagnetic if all its electrons are paired. For a transition metal ion this is decided by its d electron count, worked out from the oxidation state.
Manganate ion, \( \ce{MnO4^2-} \): x + 4(−2) = −2, so x = +6. Mn (Z = 25) is \( \mathrm{[Ar]\,3d^{5}\,4s^{2}} \); losing six electrons (two 4s, four 3d) leaves \( \mathrm{3d^{1}} \): one unpaired electron, so manganate is paramagnetic.
Permanganate ion, \( \ce{MnO4^-} \): x + 4(−2) = −1, so x = +7. Losing all seven outer electrons leaves \( \mathrm{3d^{0}} \): no unpaired electron, so permanganate is diamagnetic.
So manganate and permanganate are paramagnetic and diamagnetic, respectively.
Why the other options are incorrect
Option (1) Both are paramagnetic — Incorrect. Permanganate (\( \mathrm{3d^{0}} \)) has no unpaired electron.
Option (2) Both are diamagnetic — Incorrect. Manganate (\( \mathrm{3d^{1}} \)) has one unpaired electron.
Option (4) diamagnetic and paramagnetic — Incorrect. This reverses the two ions.
NCERT (2026-27 edition):
Oxides and Oxoanions of Metals – …
