Diamagnetism is a property exhibited by all substances, including atoms and molecules, due to the presence of electrons in their atomic or molecular orbitals. Diamagnetic substances have all their electrons paired up in their orbitals, resulting in a cancellation of magnetic moments. As a result, diamagnetic substances are weakly repelled by an external magnetic field.

Key points about diamagnetism include:

1. Paired Electrons: Diamagnetism arises from the pairing of electrons in atomic or molecular orbitals. When all electrons are paired, their magnetic moments cancel each other out.
2. Induced Magnetic Field: When a diamagnetic substance is placed in an external magnetic field, it induces a weak magnetic field in the opposite direction. This induced magnetic field opposes the applied field, causing a repulsive effect.
3. Temporary Magnetism: Diamagnetic behavior is temporary and disappears when the external magnetic field is removed.
4. Magnetic Susceptibility: Diamagnetic substances have a negative magnetic susceptibility. The magnetic susceptibility is proportional to the applied magnetic field, but in the opposite direction.
5. Examples: Most substances are diamagnetic because their electrons are paired. Noble gases, alkali metals, alkaline earth metals, and many organic molecules fall into the category of diamagnetic substances.
6. Weak Effect: Diamagnetism is a very weak effect and is often overshadowed by other stronger magnetic properties, such as paramagnetism and ferromagnetism.
7. Temperature Independence: Diamagnetic behavior is generally temperature-independent. It remains consistent regardless of changes in temperature.
8. Applications: Diamagnetism is used in various scientific techniques, such as nuclear magnetic resonance (NMR) spectroscopy, to study the electronic properties of materials.

It’s important to note that while all substances exhibit diamagnetic behavior to some extent, the effect is very weak and often masked by stronger paramagnetic or ferromagnetic effects in materials that contain unpaired electrons or exhibit long-range magnetic ordering.