Ch 4 - Introductory Chemistry, 3rd Edition Nivaldo Tro...

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Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA Introductory Chemistry , 3 rd Edition Nivaldo Tro Chapter 4 Atoms and Elements 2009, Prentice Hall
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Tro's "Introductory Chemistry", Chapter 4 2 Experiencing Atoms Atoms are incredibly small, yet they compose everything. Atoms are the pieces of elements. Properties of the atoms determine the properties of the elements.
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Tro's "Introductory Chemistry", Chapter 4 3 Experiencing Atoms There are about 91 elements found in nature. Over 20 have been made in laboratories. Each has its own, unique kind of atom. They have different structures. Therefore they have different properties.
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Tro's "Introductory Chemistry", Chapter 4 4 The Divisibility of Matter Infinitely divisible For any two points, there is always a point between. Ultimate particle Upon division, eventually a particle is reached which can no longer be divided. “Nothing exists except atoms and empty space; everything else is opinion.” - Democritus 460–370 B.C.
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Tro's "Introductory Chemistry", Chapter 4 5 Dalton’s Atomic Theory 1. Each Element is composed of tiny, indestructible particles called atoms. Tiny, hard, indivisible, spheres. 2. All atoms of an element are identical. They have the same mass, volume, and other physical and chemical properties. So, atoms of different elements are different. Every carbon atom is identical to every other carbon atom. They have the same chemical and physical properties. However, carbon atoms are different from sulfur atoms. They have different chemical and physical properties.
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Tro's "Introductory Chemistry", Chapter 4 6 Dalton’s Atomic Theory 1. Atoms combine in simple, whole-number ratios to form molecules of compounds. Because atoms are unbreakable, they must combine as whole atoms. The nature of the atom determines the ratios in which it combines. Each molecule of a compound contains the exact same types and numbers of atoms. Law of Constant Composition Chemical formulas
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Tro's "Introductory Chemistry", Chapter 4 7 Sizes of Atoms Using compositions of compounds and assumed formulas, Dalton was able to determine the relative masses of the atoms. Dalton based his scale on H = 1 amu. We now base it on C-12 = 12 amu exactly. Unit = atomic mass unit . Amu or dalton. Absolute sizes of atoms: Mass of H atom= 1.67 x 10 -24 g. Volume of H atom = 2.1 x 10 -25 cm 3 .
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Chapter 4 8 Some Notes on Charges There are two kinds of charges, called positive and negative. Opposite charges attract. + attracted to –. Like charges repel. + repels +. – repels –.
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This note was uploaded on 08/06/2011 for the course CHEM 151 taught by Professor Mcbroom during the Summer '10 term at College of the Canyons.

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Ch 4 - Introductory Chemistry, 3rd Edition Nivaldo Tro...

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