Electron

     From Wikipedia, the free encyclopedia.

Electron
Classification
Elementary particle Fermion Lepton First Generation Electron
Properties
Mass: 9.10 × 10-31 kg Electric Charge: -1.6 × 10-19C Spin: 1/2 Color Charge: none Interaction: Gravity, Electromagnetic,Weak
Wikiproject particles

The electron (sometimes also called negatron) is a subatomic particle, commonly represented as e⁻. In an atom the electrons surround the nucleus of protons and neutrons. The electron has a negative electric charge of -1.6 × 10^-19 coulombs, and a mass of about 9.10 × 10^-31 kg (0.51 MeV/c²), which is 1/1800 of the proton mass.

The electron is one of a class of subatomic particles called leptons which are believed to be fundamental particles (that is, they cannot be broken down into smaller constituent parts). The electron has spin 1/2, which implies it is a fermion, i.e., follows the Fermi-Dirac statistics. In quantum mechanics the electron is described by the Dirac Equation. In the Standard Model it forms a doublet in SU(2) with the electron neutrino, as they interact through the weak interaction. The electron has two more massive partners, with the same charge but different masses: the muon and the tau.

It is believed that the number of electrons in the known universe is 10 followed by 130 zeros. Some theorists believe the electron may be a very small black hole. See Talk:Electron.

Table of contents

1 History 2 Electricity 3 See also 4 External links

History

The electron had been posited by G. Johnstone Stoney, as a unit of charge in electrochemistry, but Thompson realised that it was also a subatomic particle.

The electron was discovereded by J.J. Thomson in 1897 at the Cavendish Laboratory at Cambridge University, while studying "cathode rays." Influenced by the work of James Clerk Maxwell, and the discovery of the X-ray, he deduced that cathode rayss existed and were negatively charged "particles", which he called "corpuscles".

Electricity

When electrons move, free of the nuclei of atoms, and there is a net flow, this flow is called electricity, or an electric current. This might be compared to a flock of sheep moving north together, while the shepherds do not. Electric charge can be directly measured with an electrometer. Electric current can be directly measured with a galvanometer.

So-called "static electricity" is not a flow of electrons at all. More correctly called a "static charge", it refers to a body that has more or fewer electrons than are required to balance the positive charge of the nuclei. When there is an excess of electrons, the object is said to be "negatively charged". When there are fewer electrons than protons, the object is said to be "positively charged". When the number of electrons and the number of protons are equal, the object is said to be electrically "neutral".

See also

• Standard model
• Subatomic particle
• Proton
• Neutron
• Photoelectric Effect
• Lightning
• List of particles

External links

• Particle Data Group