Answer: 5.
- A 5
- B 4
- C 3
- D 2
Correct answer: A. 5
Explanation: Mn (Z = 25) is [Ar]3d<sup>5</sup>4s<sup>2</sup>; Mn<sup>2+</sup> is [Ar]3d<sup>5</sup> with all five d-electrons unpaired, giving high paramagnetism.
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.