“electron”的概念、定义、翻译、参考文献-科学参考

electron

Physics

An elementary particle, classed as a lepton, with a rest mass (symbol m_e) of 9.109 3897(54)×10⁻³¹ kg and a negative charge of 1.602 177 33(49)×10⁻¹⁹ coulomb. Electrons are present in all atoms in groupings called shells around the nucleus; when they are detached from the atom they are called free electrons (see Free-electron Theory (Feature)). The antiparticle of the electron is the positron.

The electron was discovered in 1897 by Joseph John Thomson. The problem of the structure (if any) of the electron is unsolved. If the electron is taken to be a point charge, its self-energy is infinite and difficulties arise for the Lorentz–Dirac equation. It is possible to give the electron a nonzero size with a radius r₀, called the classical electron radius, given by r₀=e²/(mc²)=2.82×10⁻¹³ cm, where e and m are the charge and mass respectively of the electron and c is the speed of light. This model also causes difficulties, such as the necessity of postulating Poincaré stresses. The view put forward by superstring theory that particles such as electrons are strings in different excitation modes may solve all the difficulties associated with theories of the structure of the electron.

Astronomy

An elementary particle carrying a negative charge. Electrons are found in energy levels orbiting the nucleus of an atom. In a neutral atom, the number of electrons is equal to the number of protons. When detached from an atom they are called free electrons. Electrons have a charge of 1.602 × 10⁻¹⁹ coulomb and a mass of 9.109 × 10⁻³¹ kg. The antiparticle of the electron is the positron.

Chemistry

An elementary particle with a rest mass of 9.109 3897(54) × 10⁻³¹ kg and a negative charge of 1.602 177 33(49) × 10⁻¹⁹ coulomb. Electrons are present in all atoms in groupings called shells around the nucleus; when they are detached from the atom they are called free electrons. The antiparticle of the electron is the positron.

Chemical Engineering

A negatively charged subatomic particle with a mass of about 1/1840 of the mass of a hydrogen atom; together with protons and neutrons in the atomic nuclei it makes up an atom. The electron was identified as being a particle by British physicist Sir Joseph John Thomson FRS (1856–1940) for which he was awarded the Nobel Prize for Physics in 1906, by measuring the angles through which the cathode rays were deflected by known magnetic and electric fields. He succeeded in determining a value for the ratio of charge to mass, which was found to be constant irrespective of the nature of the cathode. The charge was determined around 1910 by American physicist and Nobel laureate for Physics Robert Millikan (1896–1953) to be 1.6 × 10⁻¹⁹ coulombs. The sharing of electrons is the main cause of chemical bonds.

Electronics and Electrical Engineering

A stable elementary particle that has a negative charge, e, of 1.602 1773 × 10^–19 coulomb, mass m of 9.109 3897 × 10^–31 kg, and spin ½. It is the natural unit of electric charge. Electrons are constituents of all atoms, moving around the nucleus in several possible or ‘allowed’ orbits (see also energy levels). They also exist independently. They are primarily responsible for electrical conduction in most materials (see energy bands). Electrons moving in one direction under the influence of an electric field constitute an electric current, the direction of conventional current flow being opposite to the direction of motion of the electrons. Electrons were first discovered as cathode rays by Sir J. J. Thomson in 1897.
Electrons are liberated by various effects: in gas-discharge tubes by the ionization of gas molecules; by heating metal filaments (thermionic emission); by the action of light, ultraviolet radiation, X-rays, or gamma-rays on matter (photoelectric effect); by the application of an intense electric field at the surface of a metal (field emission); by bombardment of a surface by high-speed electrons or positive ions (secondary emission).
Electrons experience an electric force F_E in the presence of an electric field E; moving electrons experience a transverse force F_H in the presence of a magnetic field. These have values
$F_{E} = E e$
$F_{H} = e v \times B$
where B is the magnetic flux density vector acting at right angles to v, the velocity vector. These forces are utilized in the focusing of electron beams. The electric force also accelerates the electrons.
Electrons interact with matter to produce effects dependent on the velocity of the electrons and the state of matter involved. They may undergo elastic scattering, producing deflection and localized heating due to the energy lost, or inelastic collisions, losing discrete amounts of energy and producing various phenomena: with a gas, excitation and light emission or ionization occurs; with solids and liquids, effects such as the production of X-rays, fluorescence, and secondary electron emission are observed.
An electron beam also has wavelike properties, similar to those of electromagnetic radiation, the wavelength being given by
$λ = \frac{h}{m v}$
where h is the Planck constant and mv the electron’s momentum (see also de Broglie waves).
The antiparticle of the electron is the positron, which has a positive charge and a mass equal to that of the electron.

Biology

An elementary particle present in all atoms in groupings called shells around the nucleus. When electrons are detached from the atom they are called free electrons.

Geology and Earth Sciences

Elementary particle of mass 9.11 × 10⁻³¹ kg and negative electrical charge of 1.602 × 10⁻¹⁹ C (coulombs). Electrons can exist independently, or in groups around the nucleus of an atom. Experiments show that electrons in an atom may occur at a range of distances from the nucleus but are most likely to exist in certain low-energy orbits or shells, and within these shells there are further subshells, the configuration being such that no two electrons in any one atom have identical properties. When an electron moves from one subshell to another of lower energy, electromagnetic radiation is given off; if an electron moves to a subshell of higher energy, electromagnetic radiation is absorbed. An electron moves about the nucleus in a circular or elliptical orbit and also spins on its axis.

单词	electron
释义	electron Physics An elementary particle, classed as a lepton, with a rest mass (symbol m_e) of 9.109 3897(54)×10⁻³¹ kg and a negative charge of 1.602 177 33(49)×10⁻¹⁹ coulomb. Electrons are present in all atoms in groupings called shells around the nucleus; when they are detached from the atom they are called free electrons (see Free-electron Theory (Feature)). The antiparticle of the electron is the positron. The electron was discovered in 1897 by Joseph John Thomson. The problem of the structure (if any) of the electron is unsolved. If the electron is taken to be a point charge, its self-energy is infinite and difficulties arise for the Lorentz–Dirac equation. It is possible to give the electron a nonzero size with a radius r₀, called the classical electron radius, given by r₀=e²/(mc²)=2.82×10⁻¹³ cm, where e and m are the charge and mass respectively of the electron and c is the speed of light. This model also causes difficulties, such as the necessity of postulating Poincaré stresses. The view put forward by superstring theory that particles such as electrons are strings in different excitation modes may solve all the difficulties associated with theories of the structure of the electron. Astronomy An elementary particle carrying a negative charge. Electrons are found in energy levels orbiting the nucleus of an atom. In a neutral atom, the number of electrons is equal to the number of protons. When detached from an atom they are called free electrons. Electrons have a charge of 1.602 × 10⁻¹⁹ coulomb and a mass of 9.109 × 10⁻³¹ kg. The antiparticle of the electron is the positron. Chemistry An elementary particle with a rest mass of 9.109 3897(54) × 10⁻³¹ kg and a negative charge of 1.602 177 33(49) × 10⁻¹⁹ coulomb. Electrons are present in all atoms in groupings called shells around the nucleus; when they are detached from the atom they are called free electrons. The antiparticle of the electron is the positron. Chemical Engineering A negatively charged subatomic particle with a mass of about 1/1840 of the mass of a hydrogen atom; together with protons and neutrons in the atomic nuclei it makes up an atom. The electron was identified as being a particle by British physicist Sir Joseph John Thomson FRS (1856–1940) for which he was awarded the Nobel Prize for Physics in 1906, by measuring the angles through which the cathode rays were deflected by known magnetic and electric fields. He succeeded in determining a value for the ratio of charge to mass, which was found to be constant irrespective of the nature of the cathode. The charge was determined around 1910 by American physicist and Nobel laureate for Physics Robert Millikan (1896–1953) to be 1.6 × 10⁻¹⁹ coulombs. The sharing of electrons is the main cause of chemical bonds. Electronics and Electrical Engineering A stable elementary particle that has a negative charge, e, of 1.602 1773 × 10^–19 coulomb, mass m of 9.109 3897 × 10^–31 kg, and spin ½. It is the natural unit of electric charge. Electrons are constituents of all atoms, moving around the nucleus in several possible or ‘allowed’ orbits (see also energy levels). They also exist independently. They are primarily responsible for electrical conduction in most materials (see energy bands). Electrons moving in one direction under the influence of an electric field constitute an electric current, the direction of conventional current flow being opposite to the direction of motion of the electrons. Electrons were first discovered as cathode rays by Sir J. J. Thomson in 1897. Electrons are liberated by various effects: in gas-discharge tubes by the ionization of gas molecules; by heating metal filaments (thermionic emission); by the action of light, ultraviolet radiation, X-rays, or gamma-rays on matter (photoelectric effect); by the application of an intense electric field at the surface of a metal (field emission); by bombardment of a surface by high-speed electrons or positive ions (secondary emission). Electrons experience an electric force F_E in the presence of an electric field E; moving electrons experience a transverse force F_H in the presence of a magnetic field. These have values $F_{E} = E e$ $F_{H} = e v \times B$ where B is the magnetic flux density vector acting at right angles to v, the velocity vector. These forces are utilized in the focusing of electron beams. The electric force also accelerates the electrons. Electrons interact with matter to produce effects dependent on the velocity of the electrons and the state of matter involved. They may undergo elastic scattering, producing deflection and localized heating due to the energy lost, or inelastic collisions, losing discrete amounts of energy and producing various phenomena: with a gas, excitation and light emission or ionization occurs; with solids and liquids, effects such as the production of X-rays, fluorescence, and secondary electron emission are observed. An electron beam also has wavelike properties, similar to those of electromagnetic radiation, the wavelength being given by $λ = \frac{h}{m v}$ where h is the Planck constant and mv the electron’s momentum (see also de Broglie waves). The antiparticle of the electron is the positron, which has a positive charge and a mass equal to that of the electron. Biology An elementary particle present in all atoms in groupings called shells around the nucleus. When electrons are detached from the atom they are called free electrons. Geology and Earth Sciences Elementary particle of mass 9.11 × 10⁻³¹ kg and negative electrical charge of 1.602 × 10⁻¹⁹ C (coulombs). Electrons can exist independently, or in groups around the nucleus of an atom. Experiments show that electrons in an atom may occur at a range of distances from the nucleus but are most likely to exist in certain low-energy orbits or shells, and within these shells there are further subshells, the configuration being such that no two electrons in any one atom have identical properties. When an electron moves from one subshell to another of lower energy, electromagnetic radiation is given off; if an electron moves to a subshell of higher energy, electromagnetic radiation is absorbed. An electron moves about the nucleus in a circular or elliptical orbit and also spins on its axis.
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