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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 · 2016 · Paper I

Q5(c)(i). Actinide spectra and the ligand

Question

Explain why— (i) the absorption spectra of actinides (ions) are independent of the nature of the ligand attached to them;

Answer in brief

The visible bands of actinide ions are mainly 5f→5f transitions. The 5f orbitals lie inside the filled 6s²6p⁶ shells and interact only weakly with the ligands, so the ligand field is small compared with spin–orbit coupling and electron repulsion: the levels are nearly those of the gaseous ion, and the band positions change little from ligand to ligand.

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