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🧪 Chemistry  ·  Coordination Compounds  ·  NEET & JEE

The effective atomic number (EAN) rule by Sidgwick states:

Answer: Metal in a complex acquires electrons from ligands to achieve the electron count of the next noble gas.

  • A Metal in a complex acquires electrons from ligands to achieve the electron count of the next noble gas
  • B The metal instead loses electrons to its surrounding ligands in the complex during normal conditions
  • C Ligands serve mainly to fix the oxidation state with little electron-count rule involved as generally observed
  • D The coordination number is usually numerically equal to the oxidation state in typical laboratory settings

Correct answer: A. Metal in a complex acquires electrons from ligands to achieve the electron count of the next noble gas

Explanation: Sidgwick's EAN rule: the metal + ligand electron donation brings the metal to the same electron count as the nearest noble gas.

Octahedralcoordination no. 6e.g. [Co(NH3)6]3+Tetrahedralcoordination no. 4e.g. [Ni(CO)4]Square Planarcoordination no. 4e.g. [Pt(NH3)2Cl2]

The three common coordination geometries: octahedral (6 ligands), tetrahedral (4 ligands), and square planar (4 ligands in one plane).

Concept context

Study of compounds where a central metal atom is bonded to surrounding ligands. Covers nomenclature, types of isomerism, bonding theories (VBT, CFT), and applications in medicine, photography, and industry.

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