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The electron (e −, or β − in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. [13] Electrons belong to the first generation of the lepton particle family, [14] and are generally thought to be elementary particles because they have no known components or substructure. [1]
Later these particles were identified with the electron, discovered in cathode ray experiments by J. J. Thomson in 1897. This was connected with the theoretical prediction of the electromagnetic mass by J. J. Thomson in 1881, who showed that the electromagnetic energy contributes to the mass of a moving charged body. [2]
Conversely, an electron that absorbs a photon gains energy, hence it jumps to an orbit that is farther from the nucleus. Each photon from glowing atomic hydrogen is due to an electron moving from a higher orbit, with radius r n, to a lower orbit, r m. The energy E γ of this photon is the difference in the energies E n and E m of the electron:
A simpler approach, one that has been used since the inception of quantum mechanics, is to treat charged particles as quantum mechanical objects being acted on by a classical electromagnetic field. For example, the elementary quantum model of the hydrogen atom describes the electric field of the hydrogen atom using a classical − e 2 / ( 4 π ...
1897 J. J. Thomson discovered the electron; 1897 Emil Wiechert, Walter Kaufmann and J.J. Thomson discover the electron; 1898 Marie and Pierre Curie discovered the existence of the radioactive elements radium and polonium in their research of pitchblende; 1898 William Ramsay and Morris Travers discover neon, and negatively charged beta particles
The electron was discovered between 1879 and 1897 in works of William Crookes, Arthur Schuster, J. J. Thomson, and other physicists; its charge was carefully measured by Robert Andrews Millikan and Harvey Fletcher in their oil drop experiment of 1909.
A fundamental concept of Lorentz's theory in 1895 was the "theorem of corresponding states" for terms of order v/c. This theorem states that a moving observer (relative to the ether) makes the same observations as a resting observer. This theorem was extended for terms of all orders by Lorentz in 1904.
This is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary (that is, indivisible) given the best available evidence. It also includes the discovery of composite particles and antiparticles that were of particular historical importance.