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Democritus
Democritus invented that basis of the atomic theory. His model was described as a round sphere with no proton, neutrons or electrons. -
Dalton
Dalton hypothesized that the atoms that make up different elements could be distinguished by their differences in weight. The model was described as a round, hard sphere that had no oher smaller parts. -
Thomson
Dalton discovered electrons and developed the mass spectrograph. His model was a sphere of matter in which electrons are positioned. -
Rutherford
Rutherford tested his theories using his gold foil experiment. He discovered the atomic nucleus. The model was described as a positive nucleus orbited by negative electrons (Plum Pudding model). -
Bohr
Bohr explained how electrons have stable orbits around the nucleus (Quantized shell model). -
Chadwick
Chadwick discovered the neutron. His model was similar to Bohr's in that it contains protons witha nucleus orbitted by negatively charged electrons.
