Answer: Iron (Fe 2+ ).
- A Iron (Fe<sup>2+</sup>)
- B Zinc
- C Copper
- D Manganese
Correct answer: A. Iron (Fe<sup>2+</sup>)
Explanation: Haemoglobin contains Fe<sup>2+</sup> in its haem group, which binds O<sub>2</sub> for oxygen transport in blood.
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.