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400
Democritus
First recorded person to state that all matter is made of invisible particles called atoms. -
John Dalton
Went further with the atom stating all atoms as a massed form are called elements and are pure. -
J.J. Thomson
Found the electron, but did not have it orbiting the nucleus. -
Ernest Rutherford
Studied radiation and found Uranium and Thorium. -
Period: to
Robert Milliken
Found the charge and the mass of an electron. -
Neils Bohr
Created the atomic model for the orbital shell design. -
James Chadwick
Discovered the Neutron which helped to get to today's model.
