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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 · 2016 · Mains Paper I

Q5(b). Magnetism of Gd and Tb

Question

Explain why the magnetic moment of Gd³⁺ (Z=64) complexes can be obtained by spin-only formula but not of Tb³⁺ (Z=65) complexes.

Answer in brief

Gd³⁺ has a 4f⁷, ⁸S_(7/2) ground state with L=0; Tb³⁺ has 4f⁸, ⁷F₆ with L=3, so orbital angular momentum contributes.

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CoversMagnetism of GdLanthanides

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