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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 · 2024 · Paper I

Q5(d). Relativity and lanthanide contraction

Question

Explain how 'Relativistic effect' contributes in 'Lanthanide contraction'.

Answer in brief

Poor 4f shielding is the main explanation of lanthanide contraction. Relativistic changes to penetrating electron orbitals modify screening and radial distributions and add a further contraction contribution in heavy atoms.

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Topic notes: lanthanides and actinides (lanthanide contraction, magnetic moments, separation), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverslanthanide contractionrelativistic effect4f shieldingeffective nuclear charge4d 5d size similarity

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