Which of the following statements are TRUE for the lanthanides?
\[ \begin{array}{l} \text{(A) the observed magnetic moment of Eu at room temperature is higher than that calculated from spin-orbit coupling} \\ \text{(B) Lanthanide oxides are predominantly acidic in nature} \\ \text{(C) The stability of Sm(II) is due to its half-filled sub-shell.} \\ \text{(D) Lanthanide (III) ions can be separated by ion exchange chromatography} \end{array} \]
(a)A and D
(b)A and B
(c)A and C
(d)B and C
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
Eu³⁺ has low-lying J levels populated at room temperature, so its observed moment exceeds the ground-J value. Ln(III) are separated by ion-exchange chromatography. The oxides are basic, and it is Eu(II), not Sm(II), that is stabilised by a half-filled shell. A and D (a).