- 2069 Poush
Define effective atomic number (EAN)
Short answer
EAN is the total electrons around the central metal: Z – oxidation state + 2×(number of donor electrons from ligands). Stable complexes match a noble gas; e.g., [Fe(CN)₆]⁴⁻ has EAN = 24+12 = 36 (krypton).
Define the term effective atomic number (EAN) with an example.
The effective atomic number (EAN) of a central metal is the total number of electrons around it in a complex, i.e. its own electrons (after ionisation) plus two electrons from each ligand donor.
EAN = Z − (oxidation state) + 2 × (coordination number for monodentate ligands)
According to Sidgwick, stable complexes have an EAN equal to the next noble gas.
Example: [Fe(CN)₆]⁴⁻: Fe²⁺ has 24 e⁻; adding 6 × 2 = 12 gives EAN = 36 (krypton).
✓ Answer checked by Claude Opus 5.5 (high effort)
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