Chapter Two: Early History of Chemistry. Three Important Laws. Dalton s Atomic Theory (1808) Three Important Laws (continued) Greek Explanation

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1 Greek Explanation Chapter Two: ATOMS, MOLECULES, AND IONS Notes 2.1 In the Greek model they theorized there were four elements earth, water, air, and fire. These elements were characterized by the following qualities: Earth is cold and dry; water is cold and moist; air is hot and moist; and fire is hot and dry. They even went further, assigning qualities such as love and hate to them. They theorized that these elements never existed in pure form; however, they aspired to take their proper place in the universe. Early History of Chemistry Greeks four fundamental substances Fire, earth, water, and air Democritus atomos or atom Alchemists Robert Boyle, meas. relationship of P and V of air phlogiston flowed out of burning materials Disprove phlogiston by burning Mg Antoine Lavoisier First modern book on chemistry Often called the father of modern chemistry Three Important Laws Law of conservation of mass Mass is neither created nor destroyed Law of definite proportion A given compound always contains exactly the same proportion of elements by mass Notes Three Important Laws (continued) Law of multiple proportions When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to small whole numbers. Notes 2.2 3, Practice A-D Dalton s Atomic Theory (1808) a. Each element is made up of tiny particles called atoms. b. The atoms of a given element are identical; the atoms of different elements are different in some fundamental way or ways. c. Chemical compounds are formed when atoms combine with each other. A given compound always has the same relative numbers and types of atoms. d. Chemical reactions involve reorganization of the atoms - changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction.

2 Avogadro s Hypothesis (1811) At the same temperature and pressure, equal volumes of different gases contain the same number of particles. 5 liters of oxygen 5 liters of nitrogen Same number of particles! , Practice Notes Representing Gay-Lussac s Results Representing Gay-Lussac s Results Early Experiments to Characterize the Atom Figure 2.7 A Cathode-Ray Tube J. J. Thomson - postulated the existence of electrons using cathode ray tubes. Ernest Rutherford - explained the nuclear atom, containing a dense nucleus with electrons traveling around the nucleus at a large distance. Refer to Notes

3 Figure 2.8 Deflection of Cathode Rays by an Applied Electric Field Figure 2.9 The Plum Pudding Model of the Atom Thompson s model Figure 2.10 A Schematic Representation of the Apparatus Millikan Used to Determine the Charge on the Electron Figure 2.12 Rutherford's Experiment On a-particle Bombardment of Metal Foil Figure 2.13 a & b (a) Expected Results of the Metal Foil Experiment if Thomson's Model Were Correct (b) Actual Results The Modern View of Atomic Structure The atom contains: electrons protons: found in the nucleus; positive charge equal in magnitude to the electron s negative charge. neutrons: found in the nucleus; no charge; virtually same mass as a proton. Notes 2.4,1-3

4 Table 2.1 The Mass and Charge of the Electron, Proton, and Neutron Nuclear Atom Viewed in Cross Section Fly in a cathedral analogy x 10 4 = 0.2 x 10 = x 10 Mass number (p + and n 0 ) Writing Symbols for Isotopes Atomic number (p + ) Na Element symbol Note: Because Na always has the atomic number 11, often the atomic number is not given because it is understood. Writing Symbols for Isotopes How many protons, neutrons, and electrons? Na protons = 11 p + neutrons = = 12 n 0 electrons = neutral atom, so 11 e - Notes 2.5, 4-5 Two Isotopes of Sodium Writing Symbols for Isotopes Practice 2.5 How many protons, neutrons, and electrons? Na + protons = 11 p + (same) neutrons = = 12 n 0 (same) electrons = 1+ charge, so 1 less e = 10 e - Notes 2.6

5 H is a nonmetal The Periodic Table Common Cations and Anions Notes Practice Table 2.2 The Symbols for the Elements That Are Based on the Original Names Table 2.4 Common Type II Cations Flowchart for Naming Binary Compounds Binary = two element compound Table 2.5 Common Polyatomic Ions MEMORIZE! Rules similar for naming compounds with polyatomic ions Example 2.8C

6 Table 2.6 Prefixes Used to Indicate Number in Chemical Names Table 2.7 Names of Acids* that Do Not Contain Oxygen Table 2.8 Names of Some Oxygen- Containing Acids Flowchart for Naming Acids Naming Practice Naming Practice HgO MgCl 2 Fe 2 O 3 Al(OH) 3 Na 2 O 2 Li 2 SO 3 N 2 O NO NO 2 N 2 O 3 N 2 O 4 N 2 O 5 Practice 2.8 all