important experiments leading to the discovery of subatomic particles.
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A number of historical experiments have led to the discovery of the three "elementary" particles making up atoms. The negatively charged electron was the first particle discovered. Later on, evidence that atoms were made of a small and heavy nucleus was produced. It was followed by the discovery of the positively charged proton, one of the two particles making up nucleus. The other nucleus' particle, neutron, was discovered relatively late due to its lack of electrical charge.
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ElectronThe electron is the first elementary particle to have been discovered in 1897 by J.J.Thomson (Physics Nobel Prize 1906).
Technique used: Cathode ray discharge tube |
NUcleus and protonThe proton is one of the two particles making up the nucleus of atoms. It was discovered in 1911 by Ernest Rutherford (Chemistry Nobel Prize 1908). He did an experiment in which he discovered that the atom must have a concentrated positive centre charge that contains most of the atom's mass. He also suggested that the nucleus contained a particle with a positive charge, the proton.
Technique used: Gold foil experiment |
neutronIt is the last elementary particle to have been discovered, by James Chadwick in 1932 (Physics Nobel Prize 1935).
Technique used: Bombarding alpha-particles on beryllium thin sheet |