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460
Democritus
Discovered (460-370 B.C.)
Fiest person to suggest that matter could not be ifinitely divided.
He believed "Atoms can not be created, destroyed, or further divided." -
500
Aristotle
Discovered (384-322 B.C.)
Disagreed with Democritus' idea of atoms and said that atoms don't move through empty space. -
John Dalton
Marked the beginning of the development of modern atomic theory. He took Democritus' ideas about mattter and revised them based off of his personal scientific research. Revived the term "Atom." -
Sir William Crookes
He noticed a green flash of light within a cathrode ray tube. Later he discovered that the radiation went completely through the tube and not only the Zn-S coating. Which led to the discovery of television. -
Physicist J.J. Thompson
Designed a series of CRT experiments that determined the ratio of the particles charge to its mass. Concluded that the mass of the particle was much less than that of the Hydrogen atom, which disproved Dalton's that atoms were indivisible. Discovered the electron, the first subatomic particle. -
Physicist Robert Millikan
Designed an oil drop apparatus that determined the magnitude of the electron was 1.602x10 -19 coulombs. Discovered the mass of the electron using the known charge/mass ratio 9.1x10 -28g. -
Ernest Rutherford
Studied how postively charged a particles interacted with solid matter. He designed an experiment to see if a-particles would be deflected as they passed through a thin sheet of gold foil. -
Physicist James Chadwick
Demonstrated that the nucleus had another neutral subatomic particle, the neutron.