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John Dalton
In the 1803 he suggested that each chemical element is composed of different atoms. He then decided that atoms determine the composition of matter. -
J.J. Thomson
In 1897 discovered the electron and how they had a very large charge-to-mass value. -
Ernest Rutherford
1898 He postulated the nuclear structure of the atom. He also found that atoms consist of both electrons and neutrons. He also found the nucleus in 1911. -
Robert Millikan
He determined that there was a smallest “unit” charge or that charge is quantized. -
Neils Bohr
Bohr was able to explain what happens inside an atom and was able to draw a picture of atomic structure. Receiving a Nobel prize in 1922. -
James Chadwick
Discovered a neutral atomic particle with a mass close to a neutron. -
Democritus
Proposed that all matter is made up of indestructible tiny units called atoms.
