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460 BCE
Democritus
Where he lived: Abdera, Greece.
Theory: The universe is composed of two elements: The atom and the void in which they exist and move.
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340 BCE
Aristotle
Where he lived: Stagira, Greece.
Theory: All materials on Earth are not made of atoms, but of the four elements Fire, Water, Earth, and Air.
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John Dalton
Where he lived: Manchester, U.K.
Theory: There are four parts to it. 1) All matter is composed of atoms. 2) Atoms are indivisible and indestructible. 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) Atoms combine in whole number ratios to form compounds
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J.J. Thompson
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Ernest Rutherford
Where he lived: Cambridge, U.K.
Discovery: Nucleus of the atom using the gold foil experiment.
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Niels Bohr
Where he lived: Copenhagen, Denmark.
Theory: 1) Electrons occupy certain orbits that revolve around the nucleus. 2) Each orbit has an energy associated with it. 3)Energy is absorbed when an electron jumps from a low orbit to a high one.
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Erwin Schrodinger
Where he lived: Vienna, Austria.
Theory: Quantum mechanical model. Created an equation that is used to determine the probability of finding an electron anywhere around the nucleus.
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Werner Heisenberg
Where he lived: Munich, Germany.
Theory: Uncertainty principal. Electrons do not travel in neat orbits.
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James Chadwick
Where he lived: Cambridge, U.K.
Theory: Neutrally charged particles were also in the nucleus (neutrons).
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