Information AboutElectron |
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|- | |- !align="center" bgcolor=gray|Properties |- | |- | |} The electron is a lightweight Fundamental Subatomic Particle that carries a negative Electric Charge . The electron is a spin-1/2 Lepton , does not participate in Strong Interaction s and has no substructure. Together with Atomic Nuclei , electrons make up Atom s; they are responsible for Chemical Bonding . The flow of Electricity in solid Conductor s is primarily due to the movement of electrons. Overview Within an ''. Electrons in motion constitute Electric Current , which may be used by scientists and engineers to measure many physical properties. Electric current existing for a finite time gives rise to a movement of charge ( Electricity ) that may be harnessed as a practical means to perform work. The understanding of electrons has changed dramatically over the centuries, the most significant perhaps being the development of Quantum Mechanics in the 20th century and the idea of particle/wave duality, that is, electrons can exhibit both wave-like and particle-like properties. Equally as important, Particle Physics has also furthered understanding of the electron immeasureably. The variations in Electric Field generated by differing numbers of electrons and their configurations in atoms determine the chemical properties of the Element s. These fields play a fundamental role in Chemical Bond s and Chemistry . In practice Classification The electron is one of a class of subatomic particles called Lepton s, which are believed to be Fundamental Particle s (that is, they cannot be broken down into smaller constituent parts). The word "particle" is somewhat misleading, however, because Quantum Mechanics shows that electrons also behave like a wave, e.g., in the Double-slit Experiment ; this is called Wave-particle Duality . The antiparticle of an electron is the Positron , which has the same mass but positive rather than negative charge. The discoverer of the positron, Carl D. Anderson , proposed calling standard electrons '''negatrons''', and using ''electron'' as a generic term to describe both the positively and negatively-charged variants. This usage never caught on and is rarely if ever encountered today. Properties and behavior Electrons have a negative Electric Charge of −1.6 × 10−19 Coulomb s, and a mass of about 9.11 × 10−31 kg (0.51 MeV/c2), which is approximately 1/1836 of the mass of the Proton . {Link without Title} The common electron symbol is e−. According to Quantum Mechanics , electrons can be represented by Wavefunction s, from which the Electron Density can be determined. Each electron has its own wavefunction, which is called an Orbital . The exact Momentum and position of an electron cannot be simultaneously determined. This is a limitation described by the Heisenberg Uncertainty Principle , which, in this instance, simply states that the more accurately we know a particle's position, the less accurately we can know its momentum, and vice versa. The electron has Spin ½ and is a Fermion (it obeys Fermi-Dirac Statistics ). In addition to its intrinsic angular momentum, an electron has a Magnetic Moment along its spin axis. While most electrons are found in atoms, others move independently in matter, or together as an Electron Beam in a Vacuum . In some Superconductor s, electrons move in Cooper Pair s, in which their motion is coupled to nearby matter via lattice vibrations called Phonon s. When electrons move, free of the nuclei of atoms, and there is a Net Flow , this flow is called an Electric Current . A body has a static charge when the body 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 Proton s, the object is said to be positively charged. When the number of electrons and the number of protons are equal, their charges cancel each other and the object is said to be electrically neutral. A Macroscopic body can acquire charge through rubbing, by the Phenomenon of Triboelectricity . Electrons and Positron s can Annihilate each other and produce a pair of Photon s. However, high-energy photons may transform into an electron and a positron by a process called Pair Production . The electron is an s in its vicinity, so that the properties one observes from far away are the sum of the bare properties and the vacuum effects (see Renormalization ). The Classical Electron Radius is 2.8179 × 10−15 M . This is the radius that is inferred from the electron's charge, by using the Classical theory of Electrodynamics alone, and ignoring Quantum Mechanics . It is an outdated concept that nevertheless sometimes still proves useful in calculations. Despite the utility of this constant, there is no evidence to suggest the electron actually has a radius, much less to quantify it. The speed of an electron in a Vacuum can approach, but never reach c, the Speed Of Light in a Vacuum . This is due to an effect of Special Relativity . The effects of Special Relativity are based on a quantity known as Gamma or the Lorentz Factor . Gamma is a function of v, the velocity of the particle, and c. The following is the formula for gamma: : The energy necessary to accelerate a particle is of this fast electron is 100 000 times its rest mass). Solving the equation above for the speed of the electron gives a speed of: : = 0.999 999 999 95 c. (The formula applies for large γ.) In the universe It is believed that the number of electrons existing in the known Universe is at least 1079. This number amounts to a density of about one electron per Cubic Metre of space. Based on the Classical Electron Radius and assuming a dense Sphere Packing , it can be calculated that the number of electrons that would fit in the Observable Universe is on the order of 10130. Of course, this number is even less meaningful than the classical electron radius itself. In industry Electron Beam s are used in Welding as well as Lithography . In the laboratory Early experiments The quantum or discrete nature of electron's charge was observed by Robert Millikan in the Oil-drop Experiment of 1909 . Usage Electron Microscope s are used to magnify details up to 500,000 times. Quantum effects of electrons are used in Scanning Tunneling Microscope to study features at the atomic scale. In theory In relativistic Quantum Mechanics , the electron is described by the Dirac Equation . In Quantum Field Theory , the electron is described by Quantum Electrodynamics (QED), a U(1) Gauge Theory . QED models an electron as a charged "bare" particle surrounded by a sea of interacting Virtual Particle s. These provide a correction of just over 0.1% to the predicted value of the electron's Gyromagnetic Ratio from exactly 2 (as predicted by Dirac's single-particle model). The extraordinarily precise agreement of this prediction with the experimentally determined value is viewed as one of the great achievements of modern physics. In the Standard Model of Particle Physics , the electron is the first- Generation charged Lepton . It forms a Weak Isospin doublet with the Electron Neutrino ; the two particles interact through the Weak Interaction . The electron is very similar to the two more massive particles of higher generations, the Muon and the Tau Lepton , which are identical in charge, Spin , Interaction but differ in mass. The Antimatter counterpart of the electron is the Positron . The positron has the same amount of electrical charge as the electron, except that the charge is positive. It has the same mass and spin as the electron. When an electron and a positron meet with negligible momentum, they may Annihilate each other, giving rise to two Gamma-ray photons, each having an energy of 0.511 MeV (511 KeV ). See also Electron-positron Annihilation . Electrons are also a key element in Electromagnetism , an approximate theory that is adequate for macroscopic systems, and for classical modelling of microscopic systems. History The electron as a unit of charge in electrochemistry was posited by G. Johnstone Stoney in 1874 , who also coined usage of "electron" in 1894 . During the late 1890s a number of physicists posited that electricity could be conceived of as being made of discrete units, which were given a variety of names, but their reality had not been confirmed in a compelling way. The discovery that the electron was a Subatomic Particle was made in 1897 by J.J. Thomson at the Cavendish Laboratory at Cambridge University , while he was studying " Cathode Rays ". Influenced by the work of James Clerk Maxwell , and the discovery of the X-ray , he deduced that Cathode Ray s existed and were negatively charged "''particles''", which he called "''corpuscles''." He published his discovery in 1897 . The Periodic Law states that the chemical properties of elements largely repeat themselves periodically and is the foundation of the Periodic Table of elements. The law itself was initially explained by the Atomic Mass of the elements. However, as there were anomalies in the periodic table, efforts were made to find a better explanation for it. In 1913 , Henry Moseley introduced the concept of the Atomic Number and explained the Periodic Law with the number of protons each element has. In the same year, Niels Bohr showed that electrons are the actual foundation of the table. In 1916 , Gilbert Newton Lewis explained the chemical bonding of elements by electronic interactions. See also Types of electron
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