Answer: 0 (CO is a neutral ligand).
- A 0 (CO is a neutral ligand)
- B 2+, since each CO ligand is treated as a -2/5 charge donor
- C 3+, matching iron's most common oxidation state in its salts
- D -2, as iron is formally reduced by the five CO ligands
Correct answer: A. 0 (CO is a neutral ligand)
Explanation: CO is a neutral ligand with no charge; Fe(CO)<sub>5</sub> has no overall charge, so Fe must be in the 0 oxidation state.
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.