Rutherford, Ernest (1871-1937): Born in New
Zealand, Rutherford studied under J. J. Thomson at the Cavendish Laboratory in England.
His work constituted a notable landmark in the history of atomic research as he developed Bacquerel's discovery of Radioactivity into an exact and
documented proof that the atoms of the heavier elements, which had been thought to be
immutable, actually disintegrate (decay) into various forms of radiation.
Rutherford was the first to establish the theory of the nuclear atom and to
carry out a transmutation reaction (1919) (formation of hydrogen and and oxygen isotope by
bombardment of nitrogen with alpha particles). Uranium emanations were shown to consist of
three types of rays, alpha (helium nuclei) of low penetrating power, beta (electrons), and
gamma, of exceedingly short wavelength and great energy.
Ernest Rutherford also discovered the half-life of radioactive elements and
applied this to studies of age determination of rocks by measuring the decay period of
radium to lead-206.
Henri Bacquerel (1851-1908): A French physicist who shared the
Nobel Prize in Physics with the Curies for the discovery of the radioactivity of uranium
salts. He also discovered the deflection of electrons by a magnetic field, as well as the
existence and properties of gamma radiation.