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## PowerPedia:Electron

Lasted edited by Andrew Munsey, updated on June 14, 2016 at 10:04 pm.

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The electron is a a unit of charge in electrochemistry which was posited by There was an error working with the wiki: Code[27] in There was an error working with the wiki: Code[28], who also coined the term electron in There was an error working with the wiki: Code[29]. 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. In modern science, it is a fundamental subatomic particle that carries a negative electric charge. It is a spin-½ lepton that participates in electromagnetic interactions, and its mass is less than one thousandth of that of the smallest atom. Its electric charge is defined by convention to be negative, with a value of ?1 in atomic units. Together with atomic nuclei, electrons make up atoms their interaction with adjacent nuclei is the main cause of chemical bonding.

#### History

The electron was posited by G. Johnstone Stoney in 1874, who also coined the term electron in 1894. The development of the theory of the electron s a There was an error working with the wiki: Code[30] began n 1897 by J.J. Thomson at the Cavendish Laboratory at Cambridge University, while he was studying There was an error working with the wiki: Code[31]s. A cathode ray tube is a sealed glass cylinder in which two electrodes are separated by a vacuum. When a voltage is applied across the electrodes, cathode rays are generated, causing the tube to glow. Through experimentation, Thomson discovered that the negative charge could not be separated from the rays (by the application of magnetism), and that the rays could be deflected by an electric field. He concluded that these rays, rather than being waves, were composed of negatively charged particles he called "corpuscles". He measured their mass-to-charge ratio and found it to be over a thousand times smaller than that of a hydrogen ion, suggesting that they were either very highly charged or very small in mass. Later experiments by other scientists upheld the latter conclusion.

The electron's charge was measured by There was an error working with the wiki: Code[32] in his There was an error working with the wiki: Code[33] of There was an error working with the wiki: Code[34]. The There was an error working with the wiki: Code[35] states that the chemical properties of elements largely repeat themselves periodically and is the foundation of the There was an error working with the wiki: Code[36] of elements. The law itself was initially explained by the There was an error working with the wiki: Code[37] of the elements. However, as there were anomalies in the periodic table, efforts were made to find a better explanation for it. In There was an error working with the wiki: Code[38], There was an error working with the wiki: Code[39] introduced the concept of the There was an error working with the wiki: Code[40] and explained the There was an error working with the wiki: Code[35] in terms of the number of protons each element has. In the same year, There was an error working with the wiki: Code[42] showed that electrons are the actual foundation of the table. In There was an error working with the wiki: Code[43], There was an error working with the wiki: Code[44] explained the chemical bonding of elements by electronic interactions.

#### Classification and theory

The electron is classified in mainstream science as a class of subatomic particles called There was an error working with the wiki: Code[4] coined by There was an error working with the wiki: Code[5], 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.

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In relativistic There was an error working with the wiki: Code[6]s and There was an error working with the wiki: Code[45]s . These provide a correction of just over 0.1% to the predicted value of the electron's There was an error working with the wiki: Code[46] 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 There was an error working with the wiki: Code[7] charged There was an error working with the wiki: Code[8], and There was an error working with the wiki: Code[9] but differ in mass.

The There was an error working with the wiki: Code[10] each other, giving rise to two There was an error working with the wiki: Code[11] photons. If the electron and positron had negligible momentum, each gamma ray will have an energy of 0.511 There was an error working with the wiki: Code[47]. See also There was an error working with the wiki: Code[48].

Electrons are a key element in Electromagnetism, a theory that is accurate for macroscopic systems, and for classical modelling of microscopic systems.

#### Deduced properties and behavior

Electrons have derived as to have a negative There was an error working with the wiki: Code[12] based on charge/mass measurements and a There was an error working with the wiki: Code[13]2. The mass of the electron is approximately 1/1836 of the mass of the There was an error working with the wiki: Code[49]. The common electron symbol is e&minus. http://physics.nist.gov/cgi-bin/cuu/Value?me

According to There was an error working with the wiki: Code[14] of each electron in an atom can be described by a wavefunction. Based on the There was an error working with the wiki: Code[50], the exact There was an error working with the wiki: Code[51] and position of the actual electron cannot be simultaneously determined. This is a limitation 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 There was an error working with the wiki: Code[15] ½ and is a There was an error working with the wiki: Code[52] (it follows There was an error working with the wiki: Code[53]). In addition to its intrinsic angular momentum, an electron has an intrinsic There was an error working with the wiki: Code[54] along its spin axis.

Electrons in an atom are bound to that atom electrons moving freely in vacuum, space or certain media are free electrons that can be focused into an There was an error working with the wiki: Code[16] is typically 75% of light speed.

In some There was an error working with the wiki: Code[55]s, pairs of electrons move as There was an error working with the wiki: Code[56]s in which their motion is coupled to nearby matter via lattice vibrations called There was an error working with the wiki: Code[57]s. The distance of separation between Cooper pairs is roughly 100 nm. (Rohlf, J.W.)

A body has an Electric charge when that 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 There was an error working with the wiki: Code[58]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 There was an error working with the wiki: Code[59] body can develop an electric charge through rubbing, by the There was an error working with the wiki: Code[60] of There was an error working with the wiki: Code[61].

When electrons and There was an error working with the wiki: Code[17] each other and produce pairs of high energy There was an error working with the wiki: Code[62]s or other particles. On the other hand, high-energy photons may transform into an electron and a positron by a process called There was an error working with the wiki: Code[63], but only in the presence of a nearby charged particle, such as a nucleus.

The electron is currently described as a There was an error working with the wiki: Code[18] and Mass). This effect is common to all elementary particles: Current theory suggests that this effect is due to the influence of There was an error working with the wiki: Code[64]s in its local space, so that the properties measured from a significant distance are considered to be the sum of the bare properties and the vacuum effects (see There was an error working with the wiki: Code[65]).

The There was an error working with the wiki: Code[19]. This is the radius that is inferred from the electron's electric charge, by using the There was an error working with the wiki: Code[20] theory of There was an error working with the wiki: Code[66] alone, ignoring Quantum mechanics. Classical There was an error working with the wiki: Code[66] (There was an error working with the wiki: Code[68]'s electrodynamics) is the older concept that is widely used for practical applications of electricity, electrical engineering, semiconductor physics, and electromagnetics There was an error working with the wiki: Code[69], on the other hand, is useful for applications involving modern particle physics and some aspects of optical, laser and quantum physics.

Based on current theory, the speed of an electron can approach, but never reach, c (the There was an error working with the wiki: Code[70] in a vacuum). This limitation is attributed to Einstein's theory of There was an error working with the wiki: Code[71] which defines the speed of light as a constant within all There was an error working with the wiki: Code[72]. However, when There was an error working with the wiki: Code[73] electrons are injected into a Dielectric medium, such as water, where the local speed of light is significantly less than c, the electrons will (temporarily) be traveling faster than light in the medium. As they interact with the medium, they generate a faint bluish light, called There was an error working with the wiki: Code[74].

The effects of There was an error working with the wiki: Code[21] or the There was an error working with the wiki: Code[75]. ? is a function of v, the velocity of the particle, and c. It is defined as:

:\gamma = 1 / \sqrt{1 - (v^2/c^2)}

The energy necessary to accelerate a particle is ? minus one times the rest mass. For example, the There was an error working with the wiki: Code[22] can There was an error working with the wiki: Code[76] an electron to roughly 51 GeV This gives a gamma of 100,000, since the rest mass of an electron is 0.51 MeV/c² (the [[relativistic mass] of this electron is 100,000 times its rest mass). Solving the equation above for the speed of the electron (and using an approximation for large ?) gives:

:v = \left(1-\frac {1} {2} \gamma ^{-2}\right)c = 0.999\,999\,999\,95\,c.

#### Application in the real world

Scientists believe that the number of electrons existing in the known There was an error working with the wiki: Code[77] is at least 1079. This number amounts to an average density of about one electron per There was an error working with the wiki: Code[78] of space. Astronomers have determined that 90% of all of the detectable mass in the universe is hydrogen, which is made of one electron and one proton.

Based on the There was an error working with the wiki: Code[79] and assuming a dense There was an error working with the wiki: Code[80], it can be calculated that the number of electrons that would fit in the There was an error working with the wiki: Code[81] is on the order of 10130.

There was an error working with the wiki: Code[23], There was an error working with the wiki: Code[24], There was an error working with the wiki: Code[25] and There was an error working with the wiki: Code[82] are also important tools where electrons are used.

They are also at the heart of There was an error working with the wiki: Code[83]s, which are used extensively as display devices in laboratory instruments, There was an error working with the wiki: Code[84]s and There was an error working with the wiki: Code[85]s. In There was an error working with the wiki: Code[86] tubes, one photon strikes the photocathode, initiating an avalanche of electrons that produces a detectable current.

There was an error working with the wiki: Code[87]s are used to magnify details up to 500,000 times. Quantum effects of electrons are used in There was an error working with the wiki: Code[88] to study features at the atomic scale.

#### References and external articles

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##### General information

CODATA 2002 electron mass

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The Discovery of the Electron from the American Institute of Physics History Center

Particle Data Group

Stoney, G. Johnstone, "Of the 'Electron,' or Atom of Electricity". Philosophical Magazine. Series 5, Volume 38, p. 418-420 October 1894.

Eric Weisstein's World of Physics: Electron

There was an error working with the wiki: Code[1], Wikipedia: The Free Encyclopedia. Wikimedia Foundation.

##### Notes

All masses are There was an error working with the wiki: Code[26] values accessed via the NIST’s electron mass page. The fractional version’s denominator is the inverse of the decimal value, along with its relative standard uncertainty of 4.4&nbsp×&nbsp10–10.

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