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Democritus(460BC-370BC)
He thought that the smallest particles should be called an "Atom" he also invited an atomic model. -
John Dalton(1776-1844)
Proposed an "atomic theory" with spherical solid atoms based upon measurable properities of mass. He said that 1) chemical elements are made of atoms.
2) the atoms of an element are identical in their masses
3) atoms of different elements have different masses
4) atoms only combine in small, whole number ratios such as 1:1, 1:2, 2:3 and so on.
5) atoms can be neither created nor destroyed -
Goldstein(1850-1930)
He discovered anode rays, sometimes credited with the discovery of the proton. -
J.J. Thomson(1856-1940)
He experimentedon cathode rays. He showed that cathode rays were particles with a negative electric charge and much smaller than an atom. He basically discovered electrons. -
Robert Millikan(1868-1953)
Determined the unit charge of the electron in 1909 with his oil drop experiment at the University of Chicago. Thus allowing for the calculation of the mass of the electron and positively charged atoms. -
Ernest Rutherford(1871-1937)
Proposed the nuclear atom as the result of the gold-foil experiment in 1911. In 1920, Rutherford proposed the existence of the third atomic particle, the neutron. -
Neils Bohr(1885-1962)
Contributor to understanding the structure of properities of atoms. -
Erwin Schrondinger(1887-1961)
He discovered the conduction of electricity on the surface of insulators in moist air. -
James Chadwick(1891-1974)
Discovered the neutron in 1932. Chadwick was a collab orator of Rutherford's. Interestingly the discovery of the neutron led to the discovery of fission which led to the atomic bomb.
