TRO3 Ch 4 - Chapter 4 Atoms and Elements Tro's...

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Tro's "Introductory Chemistry", Chap Chapter 4 Atoms and Elements
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Tro's "Introductory Chemistry", Chap 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", Chap 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", Chap Dalton’s Atomic Theory 1. Each Element is composed of tiny, indestructible particles called atoms. Tiny, hard, indivisible, spheres. 1. 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", Chap 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", Chap STM Image
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Tro's "Introductory Chemistry", Chap 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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Tro's "Introductory Chemistry", Chap Some Notes on Charges There are two kinds of charges, called positive and negative. Opposite charges attract. + attracted to –. Like charges repel. + repels +. – repels –. To be neutral, something must have no charge or equal amounts of opposite charges.
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Tro's "Introductory Chemistry", Chap The Atom Is Divisible Work done by J. J. Thomson and others proved that the atom had pieces called electrons . Thomson found that electrons are much smaller than atoms and carry a negative charge. The mass of the electron is 1/1836 th the mass of a hydrogen atom. The charge on the electron is the fundamental unit of charge that we call –1 charge unit.
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Tro's "Introductory Chemistry", Chap Plum Pudding Atom
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Tro's "Introductory Chemistry", Chap Rutherford’s Experiment How can you prove something is empty?
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This note was uploaded on 02/09/2011 for the course CHEM 1405 taught by Professor Kaw during the Spring '11 term at Dallas Colleges.

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TRO3 Ch 4 - Chapter 4 Atoms and Elements Tro's...

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