The discovery of the existence of the electron did not happen overnight or even once, it was the result of the work of thousands of scientists engaged in research on the structure of matter. This discovery was an event that revolutionized both chemistry and physics. We now know that the electron is a particle that has a negative charge and that it can be found in the atoms that constitute any substance, but the discovery of this particle is relatively recent; occurred at the end of the 19th century and was the result of the work developed by the English physicist J. J. Thomson, when he became interested in researching the nature and properties of certain radiations, which at the time were known as cathode rays.
In the nineteenth century, numerous scientific physicists developed experiments on the conduction of electricity through gases. Such experiments were performed most of the time with glass tubes, in which two metal plates called anode and cathode, one at each end, were applied high over them voltages. When the electric current passed through the gas in the tube, it was shown on an ammeter connected to the experimental scheme.
During the execution of the experiments, the scientists noticed an unexpected fact: the electric current was indicated in the ammeter even when a high level of vacuum was reached. Wanting to discover the reason for this phenomenon, in the year 1875, the physicist and chemist W. Crookes built a curved tube, produced a vacuum inside it and applied high voltages at its ends, where the metal plates were located. In doing so, he noticed that a certain region of the tube had a greenish luminescence. He then suspected that this luminescence was caused by some kind of radiation that the cathode emitted. These radiations were called cathode rays, however, Crookes could not determine their nature.
For many years there had been no new discoveries about cathode rays, nor had the nature of these rays been discovered. In the year 1897 J. J. Thomson performed new experiments that led him to conclude that cathode rays were formed by particles that have a negative charge. Later, Thomson proved that these rays were deflected by applying an electric field. Thus, these particles were named electrons. After discovering the nature of cathode rays, Thomson sought to determine some properties of the particles that make up the ray, for example, the charge value and mass of these particles. But it was not possible to obtain experimentally the value of these quantities, what he did was to measure the ratio between the charge and the mass of the electron.
Do not stop now... There's more after the advertising ;)
By Marco Aurélio da Silva
Brazil School Team
See more!!
Brief History of Neutron Discovery
Find out how the discovery of this particle came about
Physics - Brazil School
Would you like to reference this text in a school or academic work? Look:
SANTOS, Marco Aurélio da Silva. "The Discovery of the Electron"; Brazil School. Available in: https://brasilescola.uol.com.br/fisica/a-descoberta-eletron.htm. Accessed on June 27, 2021.
