Answer: Zn2+ ([Ar]3d10, all paired).
- A Zn2+ ([Ar]3d10, all paired)
- B Fe3+ ([Ar]3d5) in typical laboratory settings
- C Cu2+ ([Ar]3d9) under usual circumstances
- D Mn2+ ([Ar]3d5) according to most researchers
Correct answer: A. Zn2+ ([Ar]3d10, all paired)
Explanation: Zn2+ has completely filled 3d10 configuration with all electrons paired, making it diamagnetic.
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.