Ernest Rutherford
Born in New Zealand, he later studied in Cambridge under J. J. Thomson. He was awarded the Nobel Prize (chemistry) in 1908 for his researches concerning the disintegration of elements and the chemistry of radioactive substances.
However, his greatest contribution to physics was in the field of nuclear physics. Rutherford discoverd that an atom has a very small nucleus where almost all of its mass is concentrated. This discovery opened a new epoch of nuclear physics. He taught Niels Bohr at Manchester, and their collaboration was quite fruitful, leading to Bohr's atomic model. Rutherford, on the other hand, discovered that the nucleus of certain elements, such as nitrogen, could be "disintegrated" by the bombardment of alpha particles (1919), and that nitrogen in this process was transformed into oxygen. Thus Rutherford succeeded in transmuting one element into another. He suggested next year that there must be the third element, besides proton and electron, within an atom; and this third element, now called neutron, was discovered by James Chadwick in 1932.
Ironically, neutrons played an essential role both in the subsequent researches on nuclear physics and in the development of atomic bombs; but Rutherford died in 1937 before the nuclear fission was discovered (1938).
To Rutherford Page in the Nobel Foundation
See also Nuclear physics timeline