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Period: 370 to 500
Democritus
460-370 B.C
-Was the fist person to suggest that matter could be infinitely divided.
-Coined the term atomos to describe the tiny particles that make up matter and that more thru empty space. -
Period: to
John Dalton
- Took Democritus's ideas about matter and revised them based on his personal scientific research.
- Revived the term atom
- His atomic theory was widely accepted upon his ability to explain the conservation of mass.
- "atoms can be arranged, separated, or combined but cannot be created, destroyed nor divided in the process"
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Period: to
J.J Tompson
- Was a English Physists
- Designed a series of CRT (Cathode Ray Tube) experiments at Cambridge to determine the ratio of the particles charged to its mass
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Period: to
Robert Millikan
- American Physists
- Designed an oil drop apparatus to determine the charge of the electron
- Determined that the magnitude of the charge of the electron was 1.602 x 10^-19 colulombs
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Period: to
Erenst Rutherford
- Studied how positively charge particles interacted with solid matter, he designed an experiment to see if particles would be deflected as they passed thur a thin sheet of gold foil.
- Based on the results he calculated that an atom was mostly just empty space for electrons to move around.
- He claimed there was a tiny region in the center of the atom and called it the nucleus.
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Period: to
James Chadwick
- English Physists
- He demonstrated that the nucleus had another neutral subatomic particle called the neutron.
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Period: to Aug 25, 600
Aristotle
(384-322 B.C.)
- Disagreed with Democritus idea that atoms move thru empty space.
- his ideas about matter took over those of Democritus (back to square one)