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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2022 · Paper I

Q6(a). Metal–metal bonds in Cp₂Fe₂(CO)₄; structure of Bi₅³⁺

Question

(i) Calculate the number of metal–metal bonds in Cp₂Fe₂(CO)₄. (ii) Determine the structural type of the metal atom cluster Bi₅³⁺.

Answer in brief

(i) One Fe–Fe single bond: (36 − 34)/2 = 1. (ii) Bi₅³⁺ is a closo cluster with 6 skeletal pairs (n + 1): a trigonal bipyramid.

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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 →

Covers18-electron rulemetal–metal bondWade's rulescloso clusterFp dimerskeletal electron pairs

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