Chapter 2 - Chapter 2: Atoms and the Atomic Theory 2.1...

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Chapter 2: Atoms and the Atomic Theory 2.1.Early Chemical Discoveries and the Atomic Theory a) LAW OF CONSERVATION OF MASS 1) The total mass of substances present after a chemical reaction is the same as the total mass of substances before the reaction. 2) Proposed by Antoine Lavoisier in 1774. b) LAW OF CONSTANT COMPOSITION (LAW OF DEFINITE PROPORTIONS) 1) All samples of a compound have the same composition-the same proportions by mass of the constituent elements. 2) Proposed by Joseph Proust in 1799 c) DALTON’S ATOMIC THEORY 1) Each chemical element is composed of minute particles called atoms, which can be neither created nor destroyed during a chemical change. 2) All atoms of an element are alike in mass (weight) and other properties. Atoms of one element are different from those of all other elements. 3) In each of their compounds, different elements combine in a simple numerical ratio 4) Explains law of conservation of mass (same atoms must be present after a chemical reaction as before because they are indestructible) 5) Explains law of constant composition: If atoms unite in fixed numerical ratios, percent composition of a compound must be unique. 6) Law of Multiple Proportions : If two elements for more than a single compound, the masses of one element combined with a fixed mass of the second are in the ratio of small whole numbers.
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2.2. Electrons and Other Discoveries in Atomic Physics a) Certain objects display a property called electric charge. b)
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This note was uploaded on 10/26/2008 for the course CHEM 2070 taught by Professor Chirik,p during the Fall '05 term at Cornell University (Engineering School).

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Chapter 2 - Chapter 2: Atoms and the Atomic Theory 2.1...

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