The English physicist, Sir James Chadwick, 1891- 1974. Educated in Manchester, Chadwick then worked under Rutherford on research mainly with alpha particles (helium nuclei). He used data gained in these experiments to show that the positive charge of a nucleus is the same as its atomic number. In 1932, he was able to re-interpret an experiment by the Joliot-Curies, which he saw as evidence for the existence of the neutron. Chadwick's own experiments confirmed this. This discovery of the neutron allowed a massive advance in knowledge of atomic nuclei. Neutrons are the most useful particle for initiating nuclear reactions. In 1935 he received the Nobel Prize for physics.