Answer: Stable transition metal complexes have 18 electrons in the valence shell (sum of metal d electrons + ligand electrons).
- A Stable transition metal complexes have 18 electrons in the valence shell (sum of metal d electrons + ligand electrons)
- B Every transition metal atom is said to contain exactly 18 neutrons within its nucleus as frequently described in most textbook accounts
- C A maximum of 18 separate individual ligands can ever coordinate to one single metal centre during normal conditions
- D Transition metals are said to be capable of exhibiting up to 18 distinct oxidation states as generally observed in typical laboratory settings
Correct answer: A. Stable transition metal complexes have 18 electrons in the valence shell (sum of metal d electrons + ligand electrons)
Explanation: The 18-electron rule (EAN rule): stable organometallic complexes have 18 electrons in the metal valence shell (like a noble gas configuration for the metal).
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.