Choose the Incorrect statement from the following:

The correct answer is Option (2) → Diamagnetic substances are attracted by the applied magnetic field.

The magnetic behaviour of a substance depends on whether it has unpaired electrons. Diamagnetic substances (all electrons paired) are repelled by an applied magnetic field, paramagnetic substances (unpaired electrons) are attracted, and ferromagnetic substances are attracted very strongly.

• Option (1) Cr²⁺ is a stronger reducing agent than Fe²⁺. — A correct statement. Cr (Z = 24) is [Ar]3d⁵4s¹, so \( \ce{Cr^{2+}} \) is 3d⁴ and \( \ce{Cr^{3+}} \) is 3d³ (half-filled t_2g). E°(\( \ce{Cr^{3+}} \)/\( \ce{Cr^{2+}} \)) = −0.41 V is far lower than E°(\( \ce{Fe^{3+}} \)/\( \ce{Fe^{2+}} \)) = +0.77 V, so \( \ce{Cr^{2+}} \) gives up its electron much more easily.

• Option (2) Diamagnetic substances are attracted by the applied magnetic field. — The incorrect statement. Diamagnetic substances (all electrons paired) are repelled by a magnetic field.

• Option (3) E° value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺. — A correct statement. Mn (Z = 25) is [Ar]3d⁵4s², so \( \ce{Mn^{2+}} \) is 3d⁵ (half-filled, extra stable); \( \ce{Mn^{3+}} \) readily gains an electron to reach it, so E°(\( \ce{Mn^{3+}} \)/\( \ce{Mn^{2+}} \)) = +1.57 V.

• Option (4) Ferromagnetism is an extreme form of paramagnetism. — A correct statement. Ferromagnetic substances also have unpaired electrons, but their moments are aligned in domains, so the attraction is much stronger.

NCERT (2026-27 edition):
Trends in the M³⁺/M²⁺ Standard Electrode Potentials – “… The comparatively high value for Mn shows that Mn²⁺(d⁵) is particularly stable, whereas comparatively low value for Fe shows the extra stability of Fe³⁺ (d⁵). …”

Chemical Reactivity and E° Values – “… The ions Ti²⁺, V²⁺ and Cr²⁺ are strong reducing agents and will liberate hydrogen from a dilute acid …”