Physicist and winner of the Nobel prize for his discovery of the neutron.
As a boy Chadwick was a keen mathematician. It was only an administrative error on the part of Manchester University, combined with his own shyness, that caused him to be admitted to a physics rather than a mathematics degree.
Upon completing his MSc degree in 1913 Chadwick was recommended for a research scholarship which took him to the Reichsanstalt in Berlin to work with Geiger. Here he made the important discovery that radioactive b-emissions form a continuous spectrum. After the outbreak of war Chadwick was interned for four years but continued to be scientifically active, constructing experiments out of any materials he could find.
He returned to Manchester in 1918, working on radioactivity with Rutherford. He accompanied the latter to the Cavendish laboratory in Cambridge, where he remained until 1935. During his time Chadwick kicked himself for narrowly missing the discoveries of fission, the positron and artificial radioactivity.
In 1932 he discovered the neutron while researching the emissions of a-particle-bombarded beryllium. He had often considered the possibility of such a neutral particle with Rutherford, so this was no mere stroke of luck. He was awarded the Nobel Prize for this work in 1935.
After his time at the Cavendish Laboratory Chadwick initiated an accelerator programme at Liverpool University. During the Second World War he headed the British 'mission' of scientists to the Los Alamos atomic weapons project, after which he continued to be active in international and national atomic energy issues. He was knighted in 1945. He went on to become master of Gonville and Caius college, Cambridge, in 1948, taking little interest in Cambridge physics.