Free electron in physics may refer to: Electron, as a free particle Solvated electron Charge carrier, as carriers of electric charge Valence electron, as an outer shell electron that is associated with an atom Valence and conduction bands, as a conduction band electron relative to the electronic band structure of a solid Fermi gas, as a particle of a non-interacting electron gas Free electron model, as a particle in the Drude-Sommerfeld model of metals Free-electron laser, as a particle in the electron beam See also Independent electron approximation Lone pair or free electron pair Nearly free electron model Orbital angular momentum of free electrons Unpaired electron