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Electron discovered by J. J. Thomson [4] 1899 Alpha particle discovered by Ernest Rutherford in uranium radiation [5] 1900 Gamma ray (a high-energy photon) discovered by Paul Villard in uranium decay [6] 1911 Atomic nucleus identified by Ernest Rutherford, based on scattering observed by Hans Geiger and Ernest Marsden [7] 1919
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
Plaque commemorating J. J. Thomson's discovery of the electron outside the old Cavendish Laboratory in Cambridge Autochrome portrait by Georges Chevalier, 1923 Thomson c. 1920–1925 Thomson was elected a Fellow of the Royal Society (FRS) [ 24 ] [ 49 ] and appointed to the Cavendish Professorship of Experimental Physics at the Cavendish ...
Atoms were thought to be the smallest possible division of matter until 1899 when J. J. Thomson discovered the electron through his work on cathode rays. [37]: 86 [5]: 364 A Crookes tube is a sealed glass container in which two electrodes are separated by a vacuum.
This is given by λ e = h/p where h is the Planck constant and p is the momentum. [60] For the 51 GeV electron above, the wavelength is about 2.4 × 10 −17 m, small enough to explore structures well below the size of an atomic nucleus. [147]
Some particles including the positron were even discovered by using this device. By 1914, experiments by Ernest Rutherford, Henry Moseley, James Franck and Gustav Hertz had largely established the structure of an atom as a dense nucleus of positive charge surrounded by lower-mass electrons. [6]
The prevailing model of atomic structure before Rutherford's experiments was devised by J. J. Thomson. [2]: 123 Thomson had discovered the electron through his work on cathode rays [3] and proposed that they existed within atoms, and an electric current is electrons hopping from one atom to an adjacent one in a series.
The first charged lepton, the electron, was theorized in the mid-19th century by several scientists [3] [4] [5] and was discovered in 1897 by J. J. Thomson. [6] The next lepton to be observed was the muon, discovered by Carl D. Anderson in 1936, which was classified as a meson at the time. [7]