chemistry for changing times 12 th edition hill and kolb chapter 2 atoms: are they for real? john...
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Chemistry for Changing Times12th Edition
Hill and Kolb
Chapter 2Atoms: Are They for Real?
John SingerJackson Community College, Jackson, MI
© 2010 Pearson Prentice Hall Inc.
© 2010 Pearson Prentice Hall, Inc.
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Atoms: The Greek Idea
~384 B.C.E., Aristotle: All matter is composed of four elements and all matter is continuous, not atomistic.
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Atoms: The Greek Idea
~ 450 B.C.E., Leucippus and Democritus
Atomos: The point at which matter can no longer be subdivided.
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Atoms: The Greek Idea
Aristotle declared matter to be infinitely divisible.
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Lavoisier: The Law of Conservation of Mass
Early 1700s Lavoisier:
Law of Conservation of Mass: During a chemical change, matter is neither created nor destroyed.
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Lavoisier: The Law of Conservation of Mass
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1799, Proust:
Law of Definite Proportions: A compound always contains the same elements in certain definite proportions.
Proust: The Law of Definite Proportions
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Proust: The Law of Definite Proportions
Regardless of the source, copper carbonate has the same composition.
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Proust: The Law of Definite Proportions
The Berzelius experiment illustrates the Law of Definite Proportions.
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1803, John Dalton:
Law of Multiple Proportions: Elements may combine in more than one set of proportions, with each set corresponding to a different compound.
John Dalton and the Atomic Theory of Matter
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John Dalton and the Atomic Theory of Matter
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John Dalton and the Atomic Theory of Matter
• All matter is composed of extremely small particles called atoms.
• All atoms of a given element are alike and differ from the atoms of any other element.
• Compounds are formed when atoms of different elements combine in fixed proportions.
• A chemical reaction involves the rearrangement of atoms.
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Out of Chaos: The Periodic Table
1869, Dmitri Mendeleev
Mendeleev arranged the elements in order of increasing atomic mass. He left gaps for yet undiscovered elements. He also predicted the properties of those elements. When those elements were eventually discovered, many of his predictions were found to be accurate.
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Out of Chaos: The Periodic Table
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Out of Chaos: The Periodic Table
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Atoms: Real and Relevant
Atoms are a very real concept. It is even possible to observe computer-enhanced images of atoms.
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Leucippus Revisited: Molecules
Molecules are groups of atoms chemically bonded together.
A molecule of water is composed of two atoms of hydrogen (H) bonded to an atom of oxygen (O).
H2O