Lecture 3 - Chemistry: A Molecular Approach, 1st Ed....

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Chapter 2 Atoms and Elements 2008, Prentice Hall Chemistry: A Molecular Approach , 1 st Ed. Nivaldo Tro Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA
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Tro, Chemistry: A Molecular Approach 2 Scanning Tunneling Microscopy Allows a Look at Individual Atoms
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3 Dalton’s Atomic Theory (1808) 1. Elements are composed of extremely small particles called atoms . 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements. 3. Compounds are composed of atoms or ions of more than one element. The relative number of atoms of each element in a given compound is always the same. 4. Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed in chemical reactions.
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Tro, Chemistry: A Molecular Approach 4 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
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Tro, Chemistry: A Molecular Approach 5 Reaction of Sodium with Chlorine to Make Sodium Chloride 7.7 g Na + 11.9 g Cl 2 19.6 g NaCl
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Tro, Chemistry: A Molecular Approach 6 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
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Tro, Chemistry: A Molecular Approach 7 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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This note was uploaded on 05/20/2008 for the course CHEM 115 taught by Professor Larkin during the Spring '08 term at Bloomsburg.

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Lecture 3 - Chemistry: A Molecular Approach, 1st Ed....

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