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a particle with half-integral spin or an elementary excitation of a quantum system consisting of many particles, that is, a quasiparticle with half-integral spin. Fermions include all baryons—such as the proton, the neutron, and hyperons—and all leptons—the electron, the muon, and neutrinos—and the anti-particles of all baryons and leptons, as well as such quasiparticles as conduction electrons and holes in a solid. Bound systems consisting of an odd number of fermions are also fermions; examples of such systems are atomic nuclei with an odd atomic number and atoms with an odd difference between the atomic number and the number of electrons. The Pauli exclusion principle is valid for fermions. Consequently, systems consisting of identical fermions obey Fermi-Dirac statistics.
quantum stateA fundamental attribute of particles according to quantum mechanics. The quantum states are primarily x-y-z position, momentum, angular momentum, energy, spin and time.
The shell structures of the atom are made up of fermion particles, which include the protons and neutrons in the nucleus and the electrons in the outer orbits. Fermions cannot share the same quantum state variables. For example, every electron traveling in electric current has a different quantum state than the electron next to it. The fermion was named after Italian physicist Enrico Fermi (1901-1954).
Bosons are particles that can be in the same quantum state. Photons are examples of bosons, and lasers, masers and the superfluidity Helium derive their behavior as a result. The boson, pronounced "bow-son," was named after Indian physicist Satyendra Nath Bose (1894-1974). See quantum mechanics, electron, photon and Higgs boson.