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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2021 · Paper I

Q5(d). Effective atomic number rule

Question

What is EAN rule? Is this rule followed by the complexes given below? (i) Cr(CO)₆ (ii) Ni(CO)₄ (iii) Fe(CO)₉.

Answer in brief

Cr(CO)₆ and Ni(CO)₄ each have EAN 36 and obey the rule; the printed Fe(CO)₉ gives EAN 44 and is probably intended to be Fe₂(CO)₉.

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Topic notes: metal carbonyls, nitrosyls, the 18-electron and EAN rules, metal–metal bonds and clusters, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversEAN ruleeffective atomic number18-electron rulemetal carbonylsFe₂(CO)₉

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