Important Scientists in Atomic Theory
James Chadwick 1891-1974
James Chadwick discovered the neutron in 1932. When Ernest Rutherford discovered the proton scientists could tell there had to be something else in the atom, because the atomic number was less than the atomic mass. To find the neutron he put beryllium with alpha particles, which made a mysterious radiation diffuse. This radiation would discharge some of the protons in a proton rich-surface; this was discovered by Irene Joliot Curie and Fredric Joloit Curie. Then, those protons would be detected by a Geiger counter. A Geiger counter is a device that measures radiation. From there Chadwick could tell the radiation was neutral since it was not affected by the magnetic field. And since it discharged protons he knew it had to be larger than expected.
Franklin D. Roosevelt becomes president in 1932.