Lepton
A
lepton is an elementary, spin-1⁄2 particle that does not undergo strong interactions, but is subject to the Pauli exclusion principle. The best known of all leptons is the electron, which governs nearly all of chemistry as it is found in atoms and is directly tied to all chemical properties. Two main classes of leptons exist: charged leptons, and neutral leptons. Charged leptons can combine with other particles to form various composite particles such as atoms and positronium, while neutrinos rarely interact with anything, and are consequently rarely observed. There are six types of leptons, known as
flavours, forming three
generations. The first generation is the
electronic leptons, comprising the electron and electron neutrino; the second is the
muonic leptons, comprising the muon and muon neutrino; and the third is the
tauonic leptons, comprising the tau and the tau neutrino. Electrons have the least mass of all the charged leptons. The heavier muons and taus will rapidly change into electrons through a process of particle decay: the transformation from a higher mass state to a lower mass state.