Consider the ions Eu(III), Gd(III), Sm(II) and Lu(III). The observed and calculated magnetic moment values are closest for the pair
(a)Gd(III), Lu(III)
(b)Eu(III), Lu(III)
(c)Sm(III), Gd(III)
(d)Sm(III), Eu(III)
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
Gd(III) (f⁷, ⁸S₇/₂, no orbital contribution) and Lu(III) (f¹⁴, diamagnetic) have observed moments that match the calculated values; Sm(III) and Eu(III) deviate because of low-lying J states.