Sir James Chadwick discovered the neutron in 1932 by performing experiments at Cambridge’s Cavendish laboratory. Rutherford theorized that the nucleus of atoms contained positively charged protons and some neutrally charged particles. At the start of his career as a student and a scholar Chadwick was assigned, by Rutherford, the project of determining a means to compare the radioactive energy from two samples. Following this Chadwick moved to Berlin to study beta radiation, Chadwick worked with Hans Geiger, the inventor of the Geiger counter, and was able to show that beta radiation does not create discrete lines, but a continuous spectrum.
Following this Chadwick worked again with Rutherford and determined that the number of electrons surrounding the nucleus of the atom was equal to the atonic number of the atom with 1.5% margin of error. This confirmed one of the bases of atomic physics that we use today when studying chemistry, that the number of electrons orbiting a nucleus is the same as the atomic number of said atom. This was enough to propel Chadwick’s career into a directorship at the Cavendish laboratory at Cavendish.

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Chadwick was not the first to believe in the existence of the neutron, and a number of scientists had been able to come close to experimentally verifying its existence. When Rutherford had first theorized about the existence of th neutron, many scientists thought that it would be the combination of a proton and some sort of nuclear electron. The mathematics did not seem to back up this theory. Some researchers, namely Bothe and Becker, had been able to exhibit an unusual form of radiation by bombarding beryllium with alpha particles from plutonium. While many researches believed that the radiation produced by this bombardment was gamma radiation, Rutherford and Chadwick believed otherwise. Chadwick experimented, and was able to show that the radiation particles produced indeed had no charge, but they had the mass of a proton. This was indeed the neutron that’s existence had been prophesied for many years.

Chadwick continued working in science after this, after researching for a number of years at Cavendish, Chadwick proceeded to join the Manhattan project in Los Alamos and Washington by way of the British Tube Alloys project. Chadwick had expected that a nuclear bomb would be possible, although foresaw there being a number of technical and theoretical hurdles to be jumped in order to achieve this technology. In 1943 as part of the Quebec accords, Chadwick moved his research to the United States and joined the Manhattan project. James Chadwick worked some of the time in Manhattan, and was present when the Combined Policy Committee

  • Brown, Andrew. The neutron and the bomb: a biography of Sir James Chadwick. Oxford University Press, 1997.
  • Gowing, Margaret. Britain and atomic energy: 1939-1945. Macmillan, 1965.