Diamagnetic
Definition and meaning of Diamagnetic in chemistry.
Diamagnetic describes a substance that is weakly repelled by an external magnetic field because all of its electrons are paired, leaving it with no permanent magnetic moment.
In more detail
When an external magnetic field is applied, it induces small circulating currents in the paired electron clouds; by Lenz's law, these currents generate a tiny magnetic field opposing the applied one. This gives diamagnetic materials a small, negative magnetic susceptibility, so they are pushed slightly out of a magnetic field rather than pulled in. Diamagnetism is actually a property of all matter, but it is so weak that it is masked whenever unpaired electrons are present, since paramagnetic or ferromagnetic effects then dominate.
Key facts
| Field | General Chemistry |
|---|---|
| Electron requirement | All electrons paired (spin-paired) |
| Magnetic susceptibility | Small and negative (typically ~10⁻⁵ to 10⁻⁶) |
| Common examples | Water, bismuth, copper, benzene, noble gases |
Water (H2O) has only paired electrons in its molecular orbitals, so it is diamagnetic; this weak repulsion is strong enough that a live frog can be levitated inside a sufficiently powerful magnetic field.
Frequently asked questions
What is the difference between diamagnetic and paramagnetic?
Diamagnetic substances have all electrons paired and are weakly repelled by a magnetic field; paramagnetic substances have one or more unpaired electrons and are weakly attracted into a magnetic field.
Can a substance be both diamagnetic and paramagnetic?
Diamagnetism exists in every substance, but if any unpaired electrons are present the much stronger paramagnetic (or ferromagnetic) effect dominates, so the material behaves as paramagnetic overall.