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Paramagnetism of transition metals
Short answer
Paramagnetism is due to unpaired electrons with net spin magnetic moment. Transition metal ions have partly filled d orbitals, so most contain unpaired electrons and are paramagnetic. The spin-only magnetic moment is μ = √(n(n+2)) BM, where n is the number of unpaired electrons.
Why do the transition metals show paramagnetism?
Paramagnetism is the property of being weakly attracted by a magnetic field. It is due to the presence of unpaired electrons: each unpaired electron has a net spin magnetic moment (and orbital contribution) that aligns with the applied field. Substances with all electrons paired are diamagnetic (repelled weakly).
Transition metal ions have partly filled d orbitals, so most have unpaired electrons and are paramagnetic. The more unpaired electrons, the greater the paramagnetism (spin-only value shown below).
Spin-only magnetic moment: μ = √(n(n+2)) BM, where n = number of unpaired electrons.
| Ion (d-configuration) | Unpaired e⁻ (n) | μ (BM) |
|---|---|---|
| Sc²⁺/Ti³⁺ (d¹) | 1 | 1.73 |
| Ti²⁺ (d²) | 2 | 2.83 |
| V²⁺ (d³) | 3 | 3.87 |
| Cr²⁺ (d⁴) | 4 | 4.90 |
| Mn²⁺ (d⁵) | 5 | 5.92 |
| Fe²⁺ (d⁶) | 4 | 4.90 |
| Co²⁺ (d⁷) | 3 | 3.87 |
| Ni²⁺ (d⁸) | 2 | 2.83 |
| Cu²⁺ (d⁹) | 1 | 1.73 |
| Zn²⁺ (d¹⁰) | 0 | 0 (diamagnetic) |
✓ Answer checked by Claude Opus 5.5 (high effort)
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