Subatomic particle that is susceptible to the weak nuclear force but not the strong force (the force that binds an atomic nucleus together). There are six leptons: the electron, muon, tau, electron neutrino, muon neutrino, and tau neutrino.
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    An elementary particle with a unit electrical charge and a mass 1/1837 of the proton. Electrons surround the atom's positively charged nucleus and determine the atom's chemical properties.
  • Fermion - Text by M. Alan Kazlev
    Subatomic particle with half integer spin. The Pauli Exclusion Principle prevents more than one fermion occupying a particular quantum state. This means matter is conserved during particle interactions (i.e. that the net amount of fermions is a constant). The electron is considered a typical fermion, and it is because of its half-spin quality that electrons form into "shells" providing the outer valence electrons that make chemistry work, as well as making life and atoms as we know them possible. Contrast with the boson. [after physicist Enrico Fermi]
  • Hadron - Text by Anders Sandberg
    Matter particle consisting of quarks or antiquarks. Hadrons are divided into mesons, composed of a quark and an antiquark, and baryons, composed of three quarks or three antiquarks.
  • Neutrino - Text by M. Alan Kazlev; additions by Adam Getchell
    An electrically neutral lepton of spin 1/2 and extremely low mass that interacts only via the weak force and gravity and as a consequence can typically pass unimpeded through ordinary matter. A common popular illustration of this is that a burst of neutrinos could pass through a light year's thickness of lead and still retain better than two thirds of its strength. There are three known varieties in conventional matter, one in each generation of particles, associated with electron, muon, and tau leptons.
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Development Notes
Text by M. Alan Kazlev
Initially published on 03 December 2001.