Free electron

• Normally, electrons exist in energy levels (orbitals) around an atom’s nucleus. A bound electron needs to absorb enough energy to overcome the attractive force holding it to the nucleus. This energy can come from various sources:

  • Heat: Adding heat to a material increases the vibration of atoms, which can bump electrons loose. This is why metals conduct electricity better when heated.
  • Light: Light, particularly high-energy light like ultraviolet (UV) radiation, can impart enough energy to eject electrons. This is the principle behind the photoelectric effect.
  • Electric field: A strong enough electric field can accelerate electrons and provide the energy needed to escape the atom’s attraction. This is important in devices like cathode ray tubes.
  • Collisions: In high-energy collisions between atoms or molecules, electrons can be knocked free. This is relevant in processes like particle accelerators.

• Electrons in the outermost energy level (valence electrons) are generally more loosely bound and have a higher probability of being freed by these energy sources.

Free electrons play a role in many electromagnetic phenomena:

• Conduction: In metals, a large number of free electrons move relatively freely throughout the material. This allows them to carry electric current when a potential difference is applied.
• Electricity: The flow of free electrons constitutes electric current in various materials and circuits.
• Chemical Reactions: In some chemical reactions, the transfer of free electrons between atoms or molecules is what defines the reaction.