Home Education and Early Work Later Years The Neutron Manhattan Project Bibliography

Discovering the Neutron Dr. Chadwick's greatest contribution to science. “The discovery of the neutron became an important stage in the understanding of two of the fundamental forces of particle physics, the strong and weak interactions. Neutrons are also known to be important in the life-cycles of stars, especially in the neutron stars or pulsars discovered in 1967.” Dr. Rowland In 1920 Ernest Rutherford believed there was another particle in the nucleus of an atom possibly a proton electron pair with a net charge of zero, but never proved that such a particle existed. This particle was later identified by Chadwick as the neutron in 1932 and led to him receiving his Nobel Prize; this discovery was Chadwick’s greatest contribution to science. Chadwick replicated experiments of Frederic and Irene Joliot-Curie but was interested in finding the 3rd element in an atom. In the experiment he ran alpha particles into beryllium allowing the beryllium radiation to collide with paraffin wax, and then hydrogen atoms hit by the radiation were sent into a detection chamber. http://dev.physicslab.org/Document.aspx?doctype=3&filename=AtomicNuclear_ChadwickNeutron.xml Only particles with a mass very close to hydrogen would be detected because hydrogen has only one proton and one electron. An unknown particle was detected showing that indeed large neutral particles existed therefore they were names neutrons. By using this different method for tracking particle radiation he discovered the neutron, and also found it had a mass of approximately 0.1 percent more than a proton. It is 1839 times larger than an electron and carried a neutral charge. "Using kinematics, Chadwick was able to determine the velocity of the protons. Then through conservation of momentum techniques, he was able to determine that the mass of the neutral radiation was almost exactly the same as that of a proton." Catharine Colwell Finding the neutron advanced many fields of science from physics to chemistry. The neutron made an ideal bullet in physics because of its neutral charge it could penetrate deep into materials. It was used to split the uranium atom and that allowed for the release of nuclear energy agreeing with Einstein’s famous equation E=mc2. Because of this nuclear fission was possible an application Chadwick would see first-hand when he worked on the Manhattan Project building the atomic bomb.

Michael Pritchard PHYS 211X