Chadwick was born near Manchester, England, on October 20, 1891. He entered the University of Manchester in 1908 and received his bachelor 's degree from the Honours School of Physics there in 1911. He continued his studies at Manchester under Ernest Rutherford and earned a master's degree in 1913. Chadwick's work with Rutherford involved the study of radioactivity.

In 1913, Chadwick received a scholarship for graduate study, which he took with Hans Geiger at the Physikalische Technische Reichsanstalt in Berlin. When World War I began, Chadwick was interned as a civilian prisoner of war for the duration of the conflict. After the war, Chadwick rejoined Rutherford, who had become director of the Cavendish Laboratory at Cambridge.

The research for which Chadwick was awarded the Nobel Prize for physics in 1935 involved his discovery of the neutron. By 1920, scientists had discovered two subatomic particles, the proton and the electron. They had further found that the protons...