Atomic Theory Timeline
Published on Nov 22, 2015
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PRESENTATION OUTLINE
Democritus
He was the first person to propose the idea that matter was not infinitely divisible. He believed that atoms could not be created nor destroyed nor divided.
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John Dalton
Stated that if there are two elements chemically combined that they will combine in a set sequence. He proceeded to calculate atomic weights from percentage compositions of compounds, using an arbitrary system to determine the likely atomic structure of each compound. Developed the atomic theory.
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Sir William Crookes
His accidental discovery led to the invention of television. Also discovered that these electrons were negatively charged particles.
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Joseph John (JJ) Thompson
He discovered the electron. He did a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. He suggested a model of the atom as a sphere of positive matter in which electrons are positioned by electrostatic forces.
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Ernest Rutherford
He discovered alpha and beta rays, set forth the laws of radioactive decay. he postulated the nuclear structure of the atom. He created the Gold foil experiment.
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James Chadwick
Discovered the neutron. Using polonium as a source of (what he believed were) neutrons, he bombarded wax. Protons were released by the wax and Chadwick made measurements of the protons’ behavior. The protons behaved in exactly the manner they ought to if they had been hit by electrically neutral particles with a mass similar to the proton.
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Robert Millikan
Discovered the elementary electron charge. began a series of experiments to determine the electric charge carried by a single electron. He created the photoelectric effect.
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