In Depth
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Electron

The electron is a fundamental subatomic particle Subatomic particle

A subatomic particle is a particle [i] smaller than an atom [i]: it may be elementary [i] ... 

 that carries an electric charge. It is a spin- lepton that participates in electromagnetic interactions, and its mass is less than one thousandth of that of the smallest atom Atom

In chemistry [i] and physics [i], an atom is the smallest possible particle of a chemical element [i] t ... 

. Its electric charge is defined by convention to be negative, with a value of −1 in atomic units. Together with atomic nuclei Atomic nucleus

The nucleus of an atom [i] is the very dense region in its center consisting of proton [i]s and neutron [i] ... 

, electrons make up atoms; their interaction with adjacent nuclei is the main cause of chemical bonding Chemical bond

A chemical bond is the physical phenomenon of chemical species [i] being held together by attraction of ... 

.

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Timeline

1897   J. J. Thomson J. J. Thomson

Sir Joseph John Thomson, OM [i], FRS [i] often known as J. ... 

 discovers the electron as a subatomic particle Subatomic particle

A subatomic particle is a particle [i] smaller than an atom [i]: it may be elementary [i] ... 



Encyclopedia

Electron
Classification
Elementary particle
Fermion
Lepton
First Generation
Electron
 
Properties
 
Mass: 9.109 3826 × 10−31 kg Kilogram

The kilogram or kilogramme, is the SI base unit [i] of mass [i]. ... 

  1/1836.152 672 61 amu
  0.510 998 918 MeV/c Speed of light

The speed of light in a vacuum [i] is an important physical constant [i] denoted by the letter c for ... 

2
Electric Charge: −1.602 176 462 × 10−19 C
Spin:˝
Color Charge: none
Interaction: Gravity Gravitation

In physics [i], gravitation or gravity is the tendency of objects with mass [i] to accelerate [i] ... 

, Electromagnetic,
Weak Weak interaction

The weak interaction is one of the four fundamental interaction [i]s of nature. ... 


The electron is a fundamental subatomic particle Subatomic particle

A subatomic particle is a particle [i] smaller than an atom [i]: it may be elementary [i] ... 

 that carries an electric charge. It is a spin-˝ lepton that participates in electromagnetic interactions, and its mass is less than one thousandth of that of the smallest atom Atom

In chemistry [i] and physics [i], an atom is the smallest possible particle of a chemical element [i] t ... 

. Its electric charge is defined by convention to be negative, with a value of −1 in atomic units. Together with atomic nuclei Atomic nucleus

The nucleus of an atom [i] is the very dense region in its center consisting of proton [i]s and neutron [i] ... 

, electrons make up atoms; their interaction with adjacent nuclei is the main cause of chemical bonding Chemical bond

A chemical bond is the physical phenomenon of chemical species [i] being held together by attraction of ... 

.

Overview

The word electron was coined in 1891 by George Johnstone Stoney  and is derived from the term electric force introduced by William Gilbert William Gilbert

William Gilbert was born May 24 [i], 1544 [i], Colchester [i], England [i] and died... 

. Its origin is in Greek: ??e?t??? , meaning amber Amber

Amber is a fossil [i] resin [i] much used for the manufacture of ornamental objects.... 

. J.J. Thomson J. J. Thomson

Sir Joseph John Thomson, OM [i], FRS [i] often known as J.... 

 is credited with having first measured the charge/mass ratio and is considered to be the discoverer of the electron.

Within an atom, electrons surround a nucleus Atomic nucleus

The nucleus of an atom [i] is the very dense region in its center consisting of proton [i]s and neutron [i] ... 

 composed of proton Proton

In physics [i], the proton is a subatomic particle [i] with an electric charge [i] of one positive fundamental unit [i] ... 

s and neutron Neutron

In physics [i], the neutron is a subatomic particle [i] with no net electric charge [i] and a mass [i] o ... 

s in an electron configuration Electron configuration

In atomic physics [i] and quantum chemistry [i], the electron configuration is the arrangement of electron [i] ... 

. The variations in electric field Electric field

In physics [i], the properties of space that surrounds an electric charge [i] can be described using an ele ... 

 generated by differing numbers of electrons and their configurations in atoms determine the chemical properties of the element Chemical element

A chemical element, often called simply an element, is a substance [i] that can... 

s. These fields play a fundamental role in chemical bond Chemical bond

A chemical bond is the physical phenomenon of chemical species [i] being held together by attraction of ... 

s and chemistry Chemistry

Chemistry is the science [i] of matter [i] at the atom [i]ic to molecular [i] scale, dealing primarily ... 

.

Electrons in motion produce an electric current and a magnetic field Magnetic field

In physics [i], a magnetic field is that part of the electromagnetic field [i] that exists when there is ... 

. Some types of electric currents are termed electricity Electricity

Electricity is a general term for the variety of phenomena resulting from the presence and flow of electric charge [i] ... 

.

Our understanding of how electrons behave has been significantly modified during the past century, the greatest advances being the development of quantum mechanics Quantum mechanics

Quantum mechanics is a first quantized [i] quantum theory [i] that supersedes classical mechanics [i] ... 

 in the 20th century. This brought the idea of wave-particle duality Wave–particle duality

[i] exhibit [[property|properties]... 

, that is, that electrons show both wave-like and particle-like properties, to varying degrees. Equally important, particle physics Particle physics

Particle physics is a branch of physics [i] that studies the elementary [i] constitu ... 

 has furthered our understanding of how the electron interacts with other particles.

Classification

The electron is one of a class of subatomic particles called leptons, which are believed to be fundamental particles .

As with all particles, electrons can also act as waves. This is called the wave-particle duality Wave–particle duality

[i] exhibit [[property|properties]... 

, also known by the term complementarity coined by Niels Bohr Niels Bohr

Niels Bohr was a Danish [i] physicist [i] who made fundamental contributions to understanding ... 

 and can be demonstrated using the double-slit experiment Double-slit experiment

The double-slit experiment or two-slit experiment consists of letting light [i] diffract [i] ... 

.

The antiparticle of an electron is the positron Positron

The positron is the antiparticle [i] or the antimatter [i] counterpart of the electron [i]. ... 

, which has the same mass but positive rather than negative charge. The discoverer of the positron, Carl D. Anderson Carl David Anderson

Carl David Anderson was a U.S. [i] experimental physicist [i].... 

, 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 −1.6022 × 10−19 coulombs, a mass of 9.11 × 10−31 kg 1 E-31 Kg

Sorry, no overview for this topic 

 based on charge/mass measurements and a relativistic rest mass of about 0.511 MeV/c Speed of light

The speed of light in a vacuum [i] is an important physical constant [i] denoted by the letter c for ... 

2. The mass of the electron is approximately 1/1836 of the mass of the proton Proton

In physics [i], the proton is a subatomic particle [i] with an electric charge [i] of one positive fundamental unit [i] ... 

. The common electron symbol is e.

According to quantum mechanics Quantum mechanics

Quantum mechanics is a first quantized [i] quantum theory [i] that supersedes classical mechanics [i] ... 

, electrons can be represented by wavefunctions, from which a calculated probabilistic electron density Electron density

Electron density is the measure of the probability [i] of an electron [i] being present at a specific lo ... 

 can be determined. The orbital Atomic orbital

In chemistry [i], an atomic orbital is the region in which an electron [i] may be found around a single ... 

 of each electron in an atom can be described by a wavefunction. Based on the Heisenberg uncertainty principle Uncertainty principle

In quantum physics [i], the Heisenberg uncertainty principle or the Heisenberg indeterminacy principle ... 

, the exact momentum 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 spin ˝ and is a fermion . In addition to its intrinsic angular momentum, an electron has an intrinsic magnetic moment Magnetic moment

In physics [i], the magnetic moment or magnetic dipole moment is a measure of the strength of a magnetic source [i] ... 

 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 electron beam Cathode ray

Cathode rays are streams of electron [i]s observed in vacuum tube [i]s, i.e. ... 

. When free electrons move, there is a net flow Network flow

In graph theory [i], a network flow is an assignment of flow to the edges of a directed graph [i]... 

 of charge, this flow is called an electric current. The drift velocity of electrons in metal wires is on the order of mm/hour. However, the speed at which a current at one point in a wire causes a current in other parts of the wire is typically 75% of light speed.

In some superconductor Superconductivity

Superconductivity is a phenomenon occurring in certain material [i]s at extremely low temperature [i]s , ... 

s, pairs of electrons move as Cooper pairs in which their motion is coupled to nearby matter via lattice vibrations called phonon Phonon

In physics [i], a phonon is a quantized [i] mode of vibration occurring in a rigid crystal lattice [i] ... 

s. The distance of separation between Cooper pairs is roughly 100 nm.

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 proton Proton

In physics [i], the proton is a subatomic particle [i] with an electric charge [i] of one positive fundamental unit [i] ... 

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 develop an electric charge through rubbing, by the phenomenon of triboelectricity.

When electrons and positron Positron

The positron is the antiparticle [i] or the antimatter [i] counterpart of the electron [i]. ... 

s collide, they annihilate Electron-positron annihilation

Electron-positron annihilation occurs when an electron [i] and a positron [i] collide. ... 

 each other and produce pairs of high energy photon Photon

In modern physics [i], the photon is the elementary particle [i] responsible for electromagnetic phenomena [i] ... 

s or other particles. On the other hand, high-energy photons may transform into an electron and a positron by a process called pair production, but only in the presence of a nearby charged particle, such as a nucleus.

The electron is currently described as a fundamental particle or an elementary particle. It has no substructure . Hence, for convenience, it is usually defined or assumed to be a point-like mathematical point charge, with no spatial extension. However, when a test particle is forced to approach an electron, we measure changes in its properties . This effect is common to all elementary particles: Current theory suggests that this effect is due to the influence of vacuum fluctuation Virtual particle

In physics [i], a virtual particle is a particle-like abstraction used in some models of quantum field theory [i]... 

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 .

The classical electron radius is 2.8179 × 10−15 m Metre

The metre, or meter , is a measure of length [i]. ... 

. This is the radius that is inferred from the electron's electric charge, by using the classical theory of electrodynamics alone, ignoring quantum mechanics Quantum mechanics

Quantum mechanics is a first quantized [i] quantum theory [i] that supersedes classical mechanics [i] ... 

. Classical electrodynamics  is the older concept that is widely used for practical applications of electricity, electrical engineering, semiconductor physics, and electromagnetics; quantum electrodynamics Quantum electrodynamics

Quantum electrodynamics is a relativistic quantum field theory [i] of electromagnetism [i]. ... 

, 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 . This limitation is attributed to Einstein's theory of special relativity Special relativity

The special theory of relativity was proposed in 1905 [i] by Albert Einstein [i] in his article "On the Electrodynamics of Moving Bodies [i] ... 

 which defines the speed of light as a constant within all reference frames. However, when relativistic electrons are injected into a dielectric Dielectric

A dielectric, or electrical insulator [i], is a substance that is highly resistant to electric current [i] ... 

 medium, such as water, where the local speed of light is significantly less than c, the electrons will be traveling faster than light in the medium. As they interact with the medium, they generate a faint bluish light, called Cherenkov radiation Cherenkov radiation

Cherenkov radiation is electromagnetic radiation [i] emitted when a charged [i] particle [i] ... 

.

The effects of special relativity Special relativity

The special theory of relativity was proposed in 1905 [i] by Albert Einstein [i] in his article "On the Electrodynamics of Moving Bodies [i] ... 

 are based on a quantity known as ? or the Lorentz factor. ? is a function of v, the velocity of the particle, and c. It is defined as:

The energy necessary to accelerate a particle is ? minus one times the rest mass. For example, the linear accelerator at Stanford Stanford University

The Leland Stanford Junior University, commonly known as Stanford University , is a private university [i] ... 

 can accelerate Acceleration

In physics [i] or physical science, acceleration is defined as the rate of change of velocity [i].... 

 an electron to roughly 51GeV . This gives a gamma of 100,000, since the rest mass of an electron is 0.51MeV/c˛ . Solving the equation above for the speed of the electron gives:

In practice


In the universe

Scientists believe that the number of electrons existing in the known universe Universe

The term universe has a variety of meanings, based on the context in which it is used.... 

 is at least 1079. This number amounts to an average density of about one electron per cubic metre Cubic metre

The cubic metre is the SI derived unit [i] of volume [i]. ... 

 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 classical electron radius and assuming a dense sphere packing Sphere packing

In mathematics [i], sphere packing problems are problems concerning arrangements of non-overlapping iden ... 

, it can be calculated that the number of electrons that would fit in the observable universe is on the order of 10130.

In industry

Electron beam Cathode ray

Cathode rays are streams of electron [i]s observed in vacuum tube [i]s, i.e. ... 

s are used in welding, lithography, scanning electron microscope Scanning electron microscope

The scanning electron microscope is a type of electron microscope [i] capable of producing high resolut ... 

s and transmission electron microscope Transmission electron microscopy

Transmission electron microscopy is an imaging technique whereby a beam of electron [i]s is focused onto ... 

s.

They are also at the heart of cathode ray tube Cathode ray tube

The cathode ray tube or CRT, invented by German [i] physicist [i] Karl Ferdinand Braun [i] ... 

s, which are used extensively as display devices in laboratory instruments, computer monitor Computer display

[i]s in the [[larynx]... 

s and television sets. In photomultiplier Photomultiplier

Photomultiplier tubes are extremely sensitive detectors of light in the ultraviolet [i], visible [i] ... 

 tubes, one photon strikes the photocathode, initiating an avalanche of electrons that produces a detectable current.

In the laboratory

Electron microscope Electron microscope

The electron microscope is a type of microscope [i] that uses electron [i]s to create an image of the ta... 

s are used to magnify details up to 500,000 times. Quantum effects of electrons are used in Scanning tunneling microscope Scanning tunneling microscope

The scanning tunneling microscope is a non-optical microscope that scans an electrical probe over a sur... 

 to study features at the atomic scale.

In theory

In relativistic quantum mechanics Quantum mechanics

Quantum mechanics is a first quantized [i] quantum theory [i] that supersedes classical mechanics [i] ... 

, the electron can be described by the Dirac Equation which defines the electron as a point. In quantum field theory Quantum field theory

Quantum field theory is the quantum theory [i] of field [i]s.... 

, the behavior of the electron can be described by quantum electrodynamics Quantum electrodynamics

Quantum electrodynamics is a relativistic quantum field theory [i] of electromagnetism [i]. ... 

 , a U gauge theory Gauge theory

In physics [i], gauge theories are a class of physical theories based on the idea that symmetry transformation [i] ... 

. In Dirac's model, an electron is defined to be a mathematical point, a point-like, charged "bare" particle surrounded by a sea of interacting pairs of virtual particles and antiparticle Antiparticle

Corresponding to each kind of particle [i], there is an associated antiparticle with th ... 

s . These provide a correction of just over 0.1% to the predicted value of the electron's gyromagnetic ratio from exactly 2 . 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 Standard Model

The Standard Model of particle physics [i] is a theory which describes the strong [i] ... 

 of particle physics Particle physics

Particle physics is a branch of physics [i] that studies the elementary [i] constitu ... 

, the electron is the first-generation charged lepton. It forms a weak isospin doublet with the electron neutrino Neutrino

The neutrino is an elementary particle [i]. ... 

; these two particles interact with each other through the both the charged and neutral current weak interaction Weak interaction

The weak interaction is one of the four fundamental interaction [i]s of nature. ... 

. The electron is very similar to the two more massive particles of higher generations, the muon Muon

The muon is a fundamental particle [i] with negative electric charge [i] and a spin [i] of 1/2. ... 

 and the tau lepton, which are identical in charge, spin, interaction but differ in mass.

The antimatter counterpart of the electron is the positron Positron

The positron is the antiparticle [i] or the antimatter [i] counterpart of the electron [i]. ... 

. 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, they may annihilate Annihilation

Annihilation is defined as "total destruction" or "complete obliteration" of an object; having its root ... 

 each other, giving rise to two gamma-ray Gamma ray

Gamma rays are an energetic form of electromagnetic radiation [i] produced by radioactive decay [i] or ... 

 photons. If the electron and positron had negligible momentum, each gamma ray will have an energy of 0.511MeV. See also Electron-positron annihilation Electron-positron annihilation

Electron-positron annihilation occurs when an electron [i] and a positron [i] collide. ... 

.

Electrons are a key element in electromagnetism, a theory that is accurate 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 the term 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 Subatomic particle

A subatomic particle is a particle [i] smaller than an atom [i]: it may be elementary [i] ... 

 was made in 1897 by J.J. Thomson J. J. Thomson

Sir Joseph John Thomson, OM [i], FRS [i] often known as J.... 

 at the Cavendish Laboratory Cavendish Laboratory

The Cavendish Laboratory is the University of Cambridge [i]'s Department of Physics [i], and is part of ... 

 at Cambridge University University of Cambridge

name = University of Cambridge
... 

, while he was studying cathode ray tube Cathode ray tube

The cathode ray tube or CRT, invented by German [i] physicist [i] Karl Ferdinand Braun [i] ... 

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 , 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 carefully measured by Robert Millikan Robert Millikan

Robert Andrews Millikan was an American [i] experimental physicist [i] ... 

 in his oil-drop experiment Oil-drop experiment

The purpose of Robert Millikan [i]'s oil-drop experiment was to measure the electric [i] charge of the electron [i] ... 

 of 1909.

The periodic law History of the periodic table

... 

 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 Henry Moseley

Henry Gwyn Jeffreys Moseley was an English [i] physicist [i]. ... 

 introduced the concept of the atomic number and explained the periodic law History of the periodic table

... 

 in terms of the number of protons each element has. In the same year, Niels Bohr Niels Bohr

Niels Bohr was a Danish [i] physicist [i] who made fundamental contributions to understanding ... 

 showed that electrons are the actual foundation of the table. In 1916, Gilbert Newton Lewis Gilbert N. Lewis

Gilbert Newton Lewis was a famous American [i] physical chemist [i]. ... 

 explained the chemical bonding of elements by electronic interactions.

See also

  • Standard Model Standard Model

    The Standard Model of particle physics [i] is a theory which describes the strong [i] ... 

  • Subatomic particle Subatomic particle

    A subatomic particle is a particle [i] smaller than an atom [i]: it may be elementary [i] ... 

  • Fermion field
  • Lightning Lightning

    Lightning is a powerful natural electrostatic discharge [i] produced during a thunderstorm [i]. ... 

  • List of particles List of particles

    This is a list of particles in particle physics [i], including currently known and hypothetical elementary particle [i] ... 

  • Particle accelerator Particle accelerator

    A particle accelerator is a device that uses electric [i] and/or magnetic field [i]s to p ... 

  • Photoelectric effect Photoelectric effect

    The photoelectric effect is the emission of electron [i]s from matter upon the absorption of electromagnetic radiation [i]... 

  • Positron Positron

    The positron is the antiparticle [i] or the antimatter [i] counterpart of the electron [i]. ... 

  • Proton Proton

    In physics [i], the proton is a subatomic particle [i] with an electric charge [i] of one positive fundamental unit [i] ... 

  • Neutron Neutron

    In physics [i], the neutron is a subatomic particle [i] with no net electric charge [i] and a mass [i] o ... 

  • Electricity Electricity

    Electricity is a general term for the variety of phenomena resulting from the presence and flow of electric charge [i] ... 

  • Speed of light Speed of light

    The speed of light in a vacuum [i] is an important physical constant [i] denoted by the letter c for ... 

  • Balmer series

Types of electron

  • Auger electron
  • Beta ray Beta particle

    [i]s emitted by certain types of [[radioactive]... 

  • Bound electron
  • Cathode ray Cathode ray

    Cathode rays are streams of electron [i]s observed in vacuum tube [i]s, i.e. ... 

  • Core electron
  • Delocalized electron Delocalized electron

    In physics delocalized electrons are electron [i]s in a molecule [i] that are not associated with a sing ... 

  • Free electron Free electron model

    In physics [i], the free electron model is a simple model for the behaviour of electron [i]s in a crystal structure [i] ... 

  • Photo-emitted electron
  • Solvated electron
  • Valence electron Valence electron

    In chemistry [i], valence electrons are the electrons [i] located within the outermost energy level of a ... 



References



  • Brumfiel, G. . Can electrons do the splits? In Nature, 433, 11.
  • Rohlf, James William, Modern Physics from a to Z0, Wiley 1994

External links

  • from the American Institute of Physics History Center
  • Stoney, G. Johnstone, "". Philosophical Magazine. Series 5, Volume 38, p. 418-420 October 1894.
  • Eric Weisstein's World of Physics:




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