Unit 3 Vocabulary: Atomic Structure & PT Trends

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Democritus

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Ancient Greek philosopher who theorized that all matter is composed of small, indestructible units called atoms.

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John Dalton

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English chemist and physicist who developed the atomic theory of matter, proposing that each element is made of unique atoms.

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JJ Thomson

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Discovered the electron and proposed the plum pudding model of the atom.

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Ernest Rutherford

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Conducted the gold foil experiment and proposed the nuclear model of the atom, identifying the nucleus.

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Eugene Goldstein

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Discovered canal rays, which led to the identification of the proton.

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James Chadwick

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Discovered the neutron, a neutral particle within the atomic nucleus.

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Proton

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A positively charged subatomic particle found in the nucleus of an atom.

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Neutron

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A subatomic particle with no charge, found in the nucleus of an atom.

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Electron

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A negatively charged subatomic particle orbiting the nucleus of an atom.

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Mass Number

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The total number of protons and neutrons in an atom's nucleus.