The experimental magnetic moment (3.4 BM) of a hydrated salt of Eu³⁺ at 27°C is significantly different from… · ABC26IN0431
Subject: Inorganic Chemistry · Chapter: Lanthanides and Actinides · Topic: Lanthanide And Actinide – General · Exam: GATE 2005-2021 · Marks: 2 · Difficulty: Hard
The experimental magnetic moment (3.4 BM ) of a hydrated salt of $\mathrm{Eu}^{3+}$ at 27°C is significantly different from the calculated value. The difference is due to (Given: atomic number of Eu is 63)
(a)strong spin-orbit coupling.
(b)pairing of electrons in f-orbitals.
(c)population of electrons at higher J level(s) via thermal excitation.
(d)strong ligand field splitting of f-orbitals.
Answer
Answer: C ✓ checked by 4AB · confidence high
The source book printed no answer; this one was worked out and checked — see the explanation.
Explanation
Eu³⁺ (f⁶) has a ⁷F₀ ground level (μ = 0) but ⁷F₁ and ⁷F₂ lie only a few hundred cm⁻¹ higher and are thermally populated at 300 K, so the observed moment is ≈3.4 BM.