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Democritus - 400 B.C.
First man to believe that the atom was made in a circle, thought of the atom. -
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Thales of Miletus - 600 B.C.
He contributed the Cosmological thesis, which said that everything was made of water; he was also the first philosopher. -
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Aristotle - 400 B.C.
He thought that everyhting was made out of Earth, Fire, Water and Air. -
Isaac Newton - 1670
He discovered gravity, laws of motion, and the light spectrum. He thought Democritus was right about the atom. -
John Dalton - 1807
John Dalton Laws
True then false 1.) Matter is made up of atoms that are invisible and indestrituble.
False 2.) All atoms of an element are identical.
True 3.) Atoms of deifferent elements are different.
True 4.) Atoms of different elements combine in simple whole #'s to form compounds.
True 5.) Atoms cannot be created or destroyed. -
Antoine Henri Becquerel - 1896
He discovered radioactivity. He also performed the Uranium Expirerment. -
JJ Thomson - 1897
He disvocered the electron nad he said the atom cannot be a solid ball. His model was the Plum Pudidng Model. He used the Cathode Ray Tube Experirment. -
Robert Millikan - 1909
He determined the mass and charge of electrons and he performed the Oil Drop Expirement. -
Rutherford - 1911
He discovered the nucleus and is credited for the discovery of the proton. He used the Gold Foil Experirment. -
Neils Bohr - 1913
He said that electrons traveled in path and the closer the electron was to the nucleus, the less energy it took to travel and visversa. -
Francis Aston - 1919
He discovered different isotopes and performed the mass-spectrograph. -
Erwin Schrodinger - 1926
He predicted where the electrons would be at in the atom and he performed the Schrodinger's model. -
Chadwick - 1932
He proved the neutrons existense.