James Chadwick was a physicist, born October 20, 1891 in England. He was the one who discovered the null particle of atoms, the neutrons. He began his research on radioactivity at the University of Manchester in 1908. Ernest Rutherford was his supervisor.
In 1913, he won a scholarship to work in Germany and work with Hans Geiser. He could not work and was imprisoned in Germany because of World War I. He returned to work with Rutherford in 1919. Their work was directed at bombarding different elements with alpha particles.
By measuring the dispersion of the particles, they were able to determine the positive charge of the nuclei of the affected atoms. However, it was difficult to reconcile the results of their research with the knowledge, until then, of the existence of only two subatomic particles, the electron and the proton.
The idea of a very heavy neutral particle that had not yet been discovered was necessary to understand what was happening in the experiment. In 1932, by reviewing the results of an experiment by Joliot and Curie (son-in-law and daughter of scientist Marie Curie), Chadwick demonstrated that they could only be explained by the existence of a neutral particle, the neutron.
This discovery has become very useful for activating nuclear reactions in the atomic bomb and nuclear reactors. Chadwick received the Nobel Prize in Physics in 1935. In Liverpool, still in 1935, he became a professor of physics. He was director of Gonville and Caius College from 1948 to 1958.
During World War II, he helped develop atomic bombs in the United States, which were soon exploded in the Japanese cities of Hiroshima and Nagasaki. He was scientific adviser to Robert Oppenheimer, the director of the Manhattan Project (atomic bomb construction) at Los Alamos Laboratory.
Chadwick was a member of the Royal Society and many other academies in Germany and Belgium. Because his work was very important and his recognition, he was awarded the degree of Doctor Honoris causa at the Universities of Dublin, Leeds, Oxford, Birmingham, Montreal, Liverpool and Edinburgh.
He received the Copley Medal in 1950. He died on July 24, 1974 in Cambridge, England.