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UPSC Combined Geo-Scientist

Chemist

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

Mains Paper I covers inorganic chemistry.

UPSC Combined Geo-Scientist, Mains · 2022 · Mains Paper I

Q11(a). Why 4d and 5d radii are similar

Question

The atomic size increases from 3d to 4d metals. However, the atomic size is similar between 4d and 5d metals. Give reasons.

Answer in brief

The extra shell enlarges 4d atoms relative to 3d atoms. Before the 5d series, poor 4f shielding causes lanthanoid contraction, largely cancelling the expected further increase.

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Topic notes: transition elements: 3d, 4d and 5d compared, atomic radii and the lanthanide contraction, oxidation states and oxidising power, with every Civil Services, IFoS and Geo-Scientist PYQ →

Coverslanthanoid contraction4d 5d atomic radiiZr Hf similaritypoor shielding 4fperiodic trends

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