In 1909, Robert Millikan and Harvey Fletcher conducted the oil drop experiment to determine the charge of an electron.
to determine the charge of an electron.
During the 1880s and ’90s scientists searched cathode rays for the carrier of the electrical properties in matter. Their work culminated in the discovery by English physicist J.J. Thomson of the electron in 1897.
In 1932, the physicist James Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium. The resulting radiation showed high penetration through a lead shield, which could not be explained via the particles known at that time.
In 1808 John Dalton published his first general account of chemical atomic theory, a cornerstone of modern chemistry. The theory originated in his earlier studies of the properties of atmospheric gases.
|Discoverer||Year of Discovery|
|Sir James Chadwick|
|Alma mater||University of Manchester University of Cambridge|
|Known for||Discovery of the neutron MAUD Committee Report Manhattan Project|
|The quark content of a proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons.|
|Discovered||Observed as H+ by Eugen Goldstein (1886). Identified in other nuclei (and named) by Ernest Rutherford (1917–1920).|
This atomic model is known as the quantum mechanical model of the atom. In 1932, James Chadwick bombarded beryllium atoms with alpha particles.
In 1897, J.J. Thomson discovered the electron by experimenting with a Crookes, or cathode ray, tube. He demonstrated that cathode rays were negatively charged. In addition, he also studied positively charged particles in neon gas.
A consummate experimentalist, Rutherford (1871–1937) was responsible for a remarkable series of discoveries in the fields of radioactivity and nuclear physics. He discovered alpha and beta rays, set forth the laws of radioactive decay, and identified alpha particles as helium nuclei.
When passed between the poles of a magnet, these cathode rays behave the same way as the β particles described earlier. The fact that they were very small electrically charged particles led the English physicist J. J. Thomson (1856 to 1940) to identify them with the electrons of Faraday’s experiments.
|Sir J. J. Thomson OM PRS|
|Children||George Paget Thomson, Joan Paget Thomson|
What did Benjamin Franklin postulate about electricity? It was a fluid that could exist in excess, called positive, or in deficiency, called negative. … Reasoned that amount of beam’s deflection depended on mass of particles and their electric charge.