CHM131 Chpt 2

CHM131 Chpt 2 - Chapter Two ATOMS MOLECULES AND IONS 2.1...

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Chapter Two: ATOMS, MOLECULES, AND IONS 2.1 The Early History of Chemistry Chemistry has been important since ancient times. ________ were the first to try to explain why chemical changes occur (about 400 B.C.) The next 2000 years were dominated by ________________ In the 16th century foundations of _____________ chemistry were developed Robert Boyle (1627-1691) was the first chemist to perform truly _____________________________ __________________ was studied in the 17th and 18th centuries 2.2 Fundamental Chemical Laws Three Important Laws 0. Lavoisier (1743-1794) 0. ________________________________ 0. Mass is neither created nor destroyed 1. Proust (1754-1826) 1. _________________________________ 1. A given compound always contains exactly the same proportion of elements by mass (a given compound always has the same ratio of atoms) 0. Example H 2 O: Has a _____ ratio of H:O 0. John Dalton (1766-1844) 2. _________________________________ 2. 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. 2.3 Dalton’s Atomic Theory (1808) 1. Each element is made up of tiny particles called _______________. 2. The atoms of a given element are ____________________; the atoms of different elements are different in some fundamental way or ways. 3. Chemical compounds are _______ when atoms combine with each other. A given compound always has the same relative numbers and types of atoms. 4. Chemical reactions involve ________________________ of the atoms - changes in the way they are bound together. The atoms themselves are not changed in a chemical reaction. Gay-Lussac 5. In 1809 Gay-Lussac performed experiments in which he measured, under the same conditions of temperature and pressure, the volumes of gases that reacted with each other. Representing Gay-Lussac’s Results: Figure 2.4 pg 44 Avogadro’s Hypothesis (1811) 6. At the same temperature and pressure, equal volumes of different gases contain the same number of particles. 3. 5 liters of oxygen 4. 5 liters of nitrogen 5. Same number of particles! Representing Gay-Lussac’s Results: Figure 2.5 pg 45 2.4 Early Experiments to Characterize the Atom 0. J.J Thomson 1898 to 1903 studied electrical discharges in partially evacuated tubes called ______________. 0. Atoms have negative charged particles, now called __________. 1. Postulated that an atom consisted of a diffuse cloud of positive charge with negative electrons embedded randomly in it. 0. _________________________ Figure 2.9 pg 47 3. _______________________ in 1909 determined the magnitude of the electron charge in an _____________ experiment 0. Figure 2.10 pg 48
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4. ________________________ in 1896 found accidentally that a piece of mineral containing uranium could produce its image on a photographic plate in the absence of light. 1.
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CHM131 Chpt 2 - Chapter Two ATOMS MOLECULES AND IONS 2.1...

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