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14 Cards in this Set
- Front
- Back
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Electron .
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Negative charge .
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Proton .
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Positive charge .
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Neutron .
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Neutral charge .
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Atomic Mass (Decimal Number) .
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The total number neutrons in the nucleus of an atom .
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Atomic Number (Whole Number) .
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The total number of protons and electrons .
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Democritus .
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Greek philosopher , 400 B.C. Discovered an atom and found out its indivisible .
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Aristotle .
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Greek philosopher . Disagreed with Democritus .
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John Dalton .
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British chemist , 1803 . Discovered elements combine in certain proportions because they are made of single atoms . 1803: Published his atomic theory .
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JJ Thomson .
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1897 , discovered electrons . Experiment - Cathode - Ray Tube .
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Ernest Rutherford .
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1909 , discovered protons . Experiment - Gold Foil Experiment .
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Niels Bohr .
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1913 , Danish scientist . Discovered electrons move around the nucleus in certain paths , or energy levels .
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Erwin Shrödinger & Werner Heisenburg .
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20th century . Proven that the exact path of an electron can't be predicted and discovered electron clouds .
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Electron Cloud .
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Regions inside the atom where electrons are likely to be found .
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James Chadwick .
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1932 , discovered neutrons . Discovered an unknown particle in the atomic nucleus - neutron .
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