TAG | Electron discovered April 30, 1897, by Joseph John Thomson |
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| by William Atkins | |
| Wednesday, 30 April 2008 | |
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Page 1 of 2 At the time, scientists thought that the atom was the smallest indivisible part of matter that could exist. So, Thomson’s announcement, at the Royal Institution (of Great Britain) Friday Evening Discourse, on April 30, 1897, made most scientists a bit skeptical as to his startling news. In the end, the electron was the first elementary particle to be discovered. The word “electron” comes from the Greek word for “amber,” which was used by the ancient Greeks to produce an electrical charge by rubbing it onto fur, for instance, which produced a spark when brought in close proximity with a grounded object. Today, the electron is a fundamental subatomic particle that carries a negative electrical charge. Electrons, along with protons and neutrons, make up atoms. English experimental physicist Joseph John “J.J.” Thomson (1856-1940) was the director of the Cavendish Laboratory (Department of Physics), at the University of Cambridge, England, at the time of his announcement. Upon his discovery of the electron, Thomson stated, "Could anything at first sight seem more impractical than a body which is so small that its mass is an insignificant fraction of the mass of an atom of hydrogen?" [AIP: “The Discovery of Fission”] Thomson discovered the electron, a subatomic particle, through a series of experiments with cathode rays and cathode ray tubes (CRTs), which is a sealed glass cylinder with two electrodes at each end that are separated by a vacuum. Cathode rays are produced when a voltage is applied across the electrodes, which causes the tube to visibly glow. Find out more about his experiments with CRTs and the discovery of electrons, and his later Nobel Prize. Please continue on with the next page. |
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