Which of the following lanthanoid ions is diamagnetic? (At. nos. Ce = 58, Sm = 62, Eu = 63, Yb = 70)
- Eu2+
- Yb2+
- Ce2+
- Sm2+
Answer
(2) Yb2+
Solution
Eu2+: [Xe]4f7 — 7 unpaired electrons
Yb2+: [Xe]4f14 — no unpaired electron
Ce2+: [Xe]4f1 5d1 — 2 unpaired electrons
Sm2+: [Xe]4f6 — 6 unpaired electrons
∴ Only Yb2+ (completely filled 4f subshell) is diamagnetic.
Answer: (2)