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Democritus discovered that all matter is made up of invisible particles called atoms. He found that atoms are solid, insdestructable, and unique. He didn't know about a nucleus or electrons. Picture link: www.msad49.org
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John Dalton created the Atomic Theory of Matter. He discovered that elements combine at the atomic level in fixed ratios. The ratio would differ in compounds naturally because of the unique atomic weights of elements combined. He proposed the Law of Multiple Proportions. Solid sphere model. Picture link: www.epcentury.com
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He was able to identify the existence of electrons and showed that an atom can be split into even smaller parts. He found out that there are positive cores and a negative outside. Plum Pudding model. Picture link: en.wikipedia.org
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Discovered that an atom has a central positive nucleus surrounded by negative orbiting electrons. Nuclear model. Picture link: abyss.uoregon.edu
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He assumed that electrons travel in stationary orbits defined by their angular momentum and added to what Rutherford contributed. Planetary model. Picture link: www1.union.edu
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After developing theories that atoms exist. He found a way to prove that atoms exist by using his theories in quantam physics.
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Robert Millikan discovered and measured the charge of an electron. He used the Oil Drop Experiment to test his theories.
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Louis de Broglie made a contribution to Quantum model of the atom by proposing particles can possess wave-like properties. His theory helped explain how atoms, molecules, and proteins behave.
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Wolfgang Pauli proposed a principle that states that no two electrons in an atom can have the same four quantam numbers. This was known as the Pauli Exclusion Principle.
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Combined equations for the behavior or wves with the de Broglie equation to make a mathematical model for the distribution of the electrons in an atom
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Werner Heisenberg came up with the Uncertainty principle. He calculated behavior of electrons and subatomic particles that also make up an atom
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James Chadwick discovered the neutron. Modern model
