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200
440 BC -Democritus
He believes that atoms can not be divided. Atons are small, hard particles with different shapes and sizes -
201
384 BC -Aristotle
Aristotle believed that atoms could be divided. -
John Dalton
Dalton believed that all substances are made of atoms. Atoms are small paricles that cannot be created, divided, or destoryed. Atoms of the same element are exactly alike, and atoms of different elements are different. Atoms join with other atoms to make new substances. This theroy was known as the Atomic Theory. -
J.J. Thomson
He discovered electrons by the Cathode -Ray Tube Experiment. He also proposet the Plum -Pudding model showing how electrons are located throughout an atom. -
Schrodinger and Heisenbery
They discerved the Electron Clouds. Elecrtron Clouds are regions that surround the nucleus. -
Period: to
The Development of Atomic Theory
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Period: to
The Development of Atomic Theory
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Rutherford 1909
He desinged an experiment to study the parts of an atom. He aimed beam of small, positively charged particles at a thin sheet of gold foil. Rutherford put a special coating behind the foil.The coating glowed when hit by the positively charged paticles. Rutherford could then see where the particles went after hitting the gold. Some partoc;es bounced straight back, some defelected,and most passed straight through the foil. -
Rutherford 1911
Rutherford discorved a the atom's nucleus which revised the Atomic Theory. -
Bohr
Boher discovered that electrons move around the nucleus in certain pathes or energy levels. He proposed that the model for the electrons would look like a ladder.
