Pair of lanthanide ions which show significant deviation between the experimental and calculated magnetic… · ABC26IN0174
Subject: Inorganic Chemistry · Chapter: Lanthanides and Actinides · Topic: Lanthanide Contraction · Exam: CSIR NET 2019 · Marks: 2 · Difficulty: Hard
Pair of lanthanide ions which show significant deviation between the experimental and calculated magnetic moments, considering contribution from the ground state only
(a)Gd and Lu
(b)Sm and Th
(c)Eu and Tb
(d)Sm and Eu
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
For Sm³⁺ (4f⁵) and Eu³⁺ (4f⁶) the first excited J levels lie close to the ground level and are thermally populated, so the ground-state-only formula μ = g√[J(J+1)] underestimates the moment badly (Eu³⁺: calculated 0, observed ≈ 3.4 BM). Gd³⁺, Lu³⁺ and Tb³⁺ agree well.