User:Gmmin

By Gmmin

As described in the Quantum Mechanics essay, matter is made up of molecules and these, in turn are made up of atoms. A typical atom consists of a nucleus composed of positively charged protons and neutral neutrons surrounded by a cloud of orbiting negatively charged electrons

Leptons
The electron (e) is the simplest of the leptons. There are two heavier leptons called the muon (m) and the tau (t). Both are unstable and decay to simpler, more stable particles. Both have anti-particles. Muons are found in the air as cosmic rays enter the Earth's atmosphere and smash into atoms and molecules. Another type of lepton is the enigmatic neutrino (n). This was postulated in 1934 by Enrico Fermi to explain certain aspects of radioactive decay. There are three types of neutrino, each one associated with one of the three lepton described above (e, m, t). They are called the electron neutrino (ne), muon neutrino (nm), and tau neutrino (nt).

Neutrinos hardly react with other types of matter. They can easily pass through the Earth. They have no electric charge. Each one has its anti-particle version so there are six types of neutrinos. Neutrinos have a very low mass and one type can change into one of the other two types.

Leptons are never found in the nucleus of atoms. They are not subject to the Strong Nuclear Force which keeps the nucleus from flying apart. They are sometimes produced in the nucleus but are quickly expelled. Some radioactive atoms break down by a method called beta decay. During beta decay a neutron in the nucleus breaks down to give a proton (which remains in the nucleus), an electron (which flies out and causes the radioactivity of the atom) and an electron neutrino (which departs at the speed of light and is not usually detected). The atom changes to a new one since the number of protons (the Atomic Number) increases by one. Atomic Number is explained in The Elements.