Chapter2_StudentLecture_Fall09

# Chapter2_StudentLecture_Fall09 - Chapter 2 Atoms and...

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Chapter 2: Atoms and Elements Learning Objectives: 2.3 Modern Atomic Theory and the Laws 2.4 The Discovery of the Electron 2.5 The Structure of the Atom 2.6 Subatomic Particles: Protons, Neutrons, and Electrons in Atoms 2.7 The Periodic Law and the Periodic Table 2.8 Atomic Mass: The Average Mass of an Element’s Atoms 2.9 Molar Mass: Counting Atoms by Weighing Them Homework: 42, 50, 56, 60, 62, 66, 68, 70, 72, 78, 80, 84, and 88.

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Tro, Chemistry: A Molecular Approach 2 2.3 Modern atomic Theory: Law of Conservation of Mass in a chemical reaction, matter is neither created nor destroyed total mass of the materials you have before the reaction must equal the total mass of the materials you have at the end total mass of reactants = total mass of products Antoine Lavoisier 1743-1794
Tro, Chemistry: A Molecular Approach 3 Reaction of Sodium with Chlorine to Make Sodium Chloride the mass of sodium and chlorine used is determined by the number of atoms that combine since only whole atoms combine and atoms are not changed or destroyed in the process, the mass of sodium chloride made must equal the total mass of sodium and chlorine atoms that combine together 7.7 g Na + 11.9 g Cl 2 19.6 g NaCl

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Tro, Chemistry: A Molecular Approach 4 Law of Definite Proportions All samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements Joseph Proust 1754-1826
Tro, Chemistry: A Molecular Approach 5 Proportions in Sodium Chloride 54 . 1 g 39.3 g 7 . 60 Na of mass Cl of mass = = a 100.0 g sample of sodium chloride contains 39.3 g of sodium and 60.7 g of chlorine a 200.0 g sample of sodium chloride contains 78.6 g of sodium and 121.4 g of chlorine 54 . 1 g 78.6 g 21.4 1 Na of mass Cl of mass = = a 58.44 g sample of sodium chloride contains 22.99 g of sodium and 35.44 g of chlorine 541 . 1 g 22.99 g 5.44 3 Na of mass Cl of mass = =

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Tro, Chemistry: A Molecular Approach 6 Law of Multiple Proportions When two elements, (call them A and B), form two different compounds, the masses of B that combine with 1 g of A can be expressed as a ratio of small, whole numbers John Dalton 1766-1844
Tro, Chemistry: A Molecular Approach 7 Oxides of Carbon carbon combines with oxygen to form two different compounds, carbon monoxide and carbon dioxide carbon monoxide contains 1.33 g of oxygen for every 1.00 g of carbon carbon dioxide contains 2.67 g of oxygen for every 1.00 g of carbon since there are twice as many oxygen atoms per carbon atom in carbon dioxide than in carbon monoxide, the oxygen mass ratio should be 2 2 g 1.33 g 2.67 monoxide carbon in carbon of g 1 with combines that oxygen of mass dioxide carbon in carbon of g 1 with combines that oxygen of mass = =

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Tro, Chemistry: A Molecular Approach 8 Dalton’s Atomic Theory Dalton proposed a theory of matter based on it having ultimate, indivisible particles to explain these laws 1) Each element is composed of tiny, indestructible
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Chapter2_StudentLecture_Fall09 - Chapter 2 Atoms and...

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