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Antoine Lavoiser
Discovered that matter was conserved during chemical reactions. -
Period: to
History of the Atom
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John Dalton
Proposed that atoms had a measurable mass. It supported Aristotle's theory of atoms. -
Henri Becquerel
While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays. -
J.J. Thomson
Used a cathode ray tube to determine the electron's charge to mass ratio which is 1.759X10^8 coulombs/gram. -
The Curies
Discovered the elements polonium and thorium and also that certain elements were radioactive. The more radioactive, the shorter the half life. -
Max Planck
Theory of quanta or that energy was released in little packets instead of one continuous stream. -
Robert Millikan
Discovered the electron charge and mass with an oil drop experiment. Supporting J.J. Thomson's theory even more. -
Rutherford
Shot alpha particles at a thin gold film and realized that a few bounced back. Thus proposing the idea of a dense positively charged proton. -
Niels Bohr
Made the Bohr model and disproved the previouse theory of an atom's composition by placing the atoms on the outside in different layers. -
Mosley
Used x-ray tubes to find the charge of an atom's nucleus. It was supported by Rutherford's theory of a positively charged nucleus. -
Werner Heisenberg
Principle of Indeterminacy you can’t know the position and velocity of something at the same time. -
Erwin Schrodinger
Proposed the idea that electrons are outside of the atome in a "cloud" formation. Based on Bohr's theory of an atom. -
James Chadwick
Found that there were also particles with no charge in the nucleus called neutrons.
