Intermediate Topic 180 of 1102 Bonding & Molecular Structure
Paramagnetism
Property of substances with unpaired electrons that are attracted into magnetic fields.
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In-depth explanation of Paramagnetism
Paramagnetism occurs in substances that contain unpaired electrons. Their magnetic moments align with an applied field and draw the sample into it. The effect is typically much stronger than diamagnetism, and it weakens with temperature because thermal motion randomizes the alignment. The spin-only magnetic moment for n unpaired electrons is mu = sqrt(n(n+2)) Bohr magnetons, which allows the number of unpaired electrons to be estimated from measured magnetism. Transition metal complexes and free radicals are typical paramagnetic species.
Going deeper: Paramagnetism
Key ideas: Number of unpaired electrons n gives mu equal to square root of n(n+2) Bohr magnetons: n=1 gives 1.73, n=2 gives 2.83, n=3 gives 3.87, n=4 gives 4.90, n=5 gives 5.92. Use it to decide between high and low spin in complexes: Fe2+ in octahedral complexes has 4 unpaired electrons for high spin and 0 for low spin. Measured by a Gouy balance.
Common mistakes and connections: Common errors are counting paired electrons, using the formula with n instead of n+2, or forgetting that the moment is spin-only and orbital contributions matter for some ions. Do not state that paramagnetism implies a permanent magnet: ferromagnets are a separate cooperative phenomenon. Links to hybridization, crystal field theory and EPR spectroscopy.
Visualization of Paramagnetism
Paramagnetism grows with the number of unpaired electrons. Fe3+ and Mn2+ with five unpaired d electrons are strongly paramagnetic, but Zn2+ is not. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Fe3+ with five unpaired electrons has a spin-only magnetic moment of about 5.9 Bohr magnetons.
Frequently asked questions about Paramagnetism
What is Paramagnetism?
Property of substances with unpaired electrons that are attracted into magnetic fields.
Is Paramagnetism a beginner, intermediate or advanced topic?
Paramagnetism is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
What should I learn before Paramagnetism?
Study these earlier topics in Bonding & Molecular Structure first: MO Diagram of Homonuclear Diatomics, Paramagnetism of Oxygen, Diamagnetism.
What comes after Paramagnetism?
The next topics in Bonding & Molecular Structure are Heteronuclear Diatomic MOs and Delocalization.
Can I practise Paramagnetism with quizzes?
Yes. The interactive lesson includes a self-check question on Paramagnetism, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Where Paramagnetism fits in Bonding & Molecular Structure
Paramagnetism is topic 65 of 104 in Bonding & Molecular Structure.