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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 · 2024 · Paper I

Q2(b)(ii). Molecular orbital diagram of CO

Question

Draw the molecular orbital diagram for CO.

Answer in brief

CO has 10 valence electrons, (3σ)²(4σ)²(1π)⁴(5σ)², bond order 3; the HOMO (5σ) is a lone pair on carbon and the LUMO (2π) is an empty π* orbital.

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As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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Topic notes: molecular orbital theory: LCAO, MO diagrams of N₂, O₂, CO, NO, CN⁻ and HF, bond order and magnetism, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversMO diagram of COHOMO LUMOs–p mixingcarbon monoxidesynergic bondingbond order

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