Answer: Mn2+.
- A Ti3+
- B Mn2+
- C Fe2+
- D Ni2+
Correct answer: B. Mn2+
Explanation: Mn2+ is 3d5 with 5 unpaired electrons; Ti3+ (d1), Fe2+ (d6, 4 unpaired) and Ni2+ (d8, 2 unpaired) have fewer.
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.