1. Pm³⁺ and Sm³⁺ 2. Ce⁴⁺ and Yb²⁺ 3. Ce³⁺ and Eu²⁺ 4. Gd³⁺ and Eu³⁺

Answer: 2. Ce⁴⁺ and Yb²⁺ Key idea: diamagnetic means no unpaired electrons, so 4f⁰ or 4f¹⁴ . mathrmCe⁴⁺ : 4f⁰ ; mathrmYb²⁺ : 4f¹⁴ . Both diamagnetic. mathrmPm³⁺ ( f⁴ ), mathrmSm³⁺ ( f⁵ ), mathrmCe³⁺ ( f¹ ), mathrmEu²⁺ ( f⁷ ), mathrmGd³⁺ ( f⁷ ), mathrmEu³⁺ ( f⁶ ) are paramagnetic. Option 2.

Topic: Lanthanoids and lanthanoid contraction· d- and f-Block Elements

The pair of lanthanoid ions which are diamagnetic is

1. \(Pm^{3+}\) and \(Sm^{3+}\)

2. \(Ce^{4+}\) and \(Yb^{2+}\)

3. \(Ce^{3+}\) and \(Eu^{2+}\)

4. \(Gd^{3+}\) and \(Eu^{3+}\)

Doubtly Asked 30 Oct 2026 NEET UG 2024 Practice test neet Save WhatsApp Report

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Answer: 2. \(Ce^{4+}\) and \(Yb^{2+}\)

Key idea: diamagnetic means no unpaired electrons, so \(4f^0\) or \(4f^{14}\).

\(\mathrm{Ce^{4+}}\): \(4f^0\); \(\mathrm{Yb^{2+}}\): \(4f^{14}\). Both diamagnetic.
\(\mathrm{Pm^{3+}}\) (\(f^4\)), \(\mathrm{Sm^{3+}}\) (\(f^5\)), \(\mathrm{Ce^{3+}}\) (\(f^1\)), \(\mathrm{Eu^{2+}}\) (\(f^7\)), \(\mathrm{Gd^{3+}}\) (\(f^7\)), \(\mathrm{Eu^{3+}}\) (\(f^6\)) are paramagnetic.

Option 2.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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The pair of lanthanoid ions which are diamagnetic is

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