Answer: Mn 2+ (d 5 ) has an extra-stable half-filled 3d subshell.
- A Mn<sup>3+</sup> already has a stable half-filled configuration
- B Mn<sup>3+</sup> is strongly hydrated
- C Mn<sup>2+</sup> (d<sup>5</sup>) has an extra-stable half-filled 3d subshell
- D Mn<sup>2+</sup> is a strong oxidising agent
Correct answer: C. Mn<sup>2+</sup> (d<sup>5</sup>) has an extra-stable half-filled 3d subshell
Explanation: Mn<sup>2+</sup> is d<sup>5</sup> (half-filled, extra stable), so the reduction Mn<sup>3+</sup> to Mn<sup>2+</sup> is highly favourable, giving a large positive E°.
Aqueous solutions of transition metal ions show characteristic colours caused by electrons absorbing visible light to jump between split d-orbitals; the exact colour depends on the metal, its oxidation state, and surrounding ligands.
Concept context
Transition metals (d-block) and lanthanides/actinides (f-block). Known for coloured compounds, variable oxidation states, complex formation, and catalytic properties. Frequently tested in JEE and NEET.