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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 · 2023 · Mains Paper I

Q10(b). Lanthanoid contraction and hydroxide basicity

Question

What is lanthanide contraction? How does it account for higher basicity of La(OH)₃ compared to Lu(OH)₃?

Answer in brief

Lanthanoid contraction is the gradual decrease in size, especially of Ln³⁺, from La to Lu. Larger La³⁺ gives a more ionic and more basic hydroxide than smaller Lu³⁺.

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

Coverslanthanide contractionbasicity of lanthanide hydroxidesLa(OH)3 vs Lu(OH)34f shieldingpolarising power

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