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Period: 300 to
timespan
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400
Aristotle BC
Aritotles believe that matter was made of "The Four Elements" http://www.timetoast.com/timelines/the-atom-timeline -
460
Democritus BC
Democritus said that all matter is composed of atoms. http://www.timetoast.com/timelines/democritus-atom -
Dalton
Dalton said that atoms are the smallest unit of matter and cannot be broken down, and he discovered the atomic theory. http://www.timetoast.com/timelines/the-atom-timeline -
Thomson
Dalton discovered the electron using the cathode-ray tube. http://www.timetoast.com/timelines/the-atom-timeline -
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Bohr
He made a model to show the number of electrons. http://www.timetoast.com/timelines/the-atom-timeline -
Schrodinger
He made an equation for quantum wave mechanics. http://www.timetoast.com/timelines/the-atom-timeline -
Heisenberg
He made the "uncertainty principle" which is the fact that one can't measure where a particle is or where it will go. http://www.timetoast.com/timelines/the-atom-timeline
