Chapter 2 - Atomic Theory, Periodic Table, & Nomenclature (1)

Chapter 2 - Atomic Theory, Periodic Table, & Nomenclature (1)

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GENERAL CHEMISTRY CHAP 2 – ATOMIC THEORY, PERIODIC TABLE, & NOMEN PAGE 1 OF 25 The History of Chemistry Early Philosophy of Matter (400 B.C.) The Greeks were the first to explain why chemical changes Proposed that all fundamental matter was composed of (4) fundamental substances: Fire Earth Water Air Some philosophers (Leucippus and Democritus) believed that matter had an ultimate, tiny, indivisible particle Other philosophers (Plato and Aristotle) believed that matter was infinitely divisible The Greeks had no experiments to test their ideas so no conclusion could be made about the divisibility of matter Since there was no experimental way of proving who was correct, the best debater was the person assumed correct Aristotle Next 2000 Years Chemistry was dominated by a “pseudoscience” called alchemy Alchemists were mystics and fakes with the idea of turning cheap metal into gold The alchemists discovered several elements and learned to prepare mineral acids Antoine Lavoisier (1743-1794) Antoine Lavoisier, a French chemist, explained the true nature of combustion He performed experiments which he carefully weighed the reactants and products from various reactions From these experiments, he suggested “mass is neither created nor destroyed The total mass of the materials you have before the reaction must equal the total mass of the materials you have at the end Law of Conservation of Mass
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GENERAL CHEMISTRY CHAP 2 – ATOMIC THEORY, PERIODIC TABLE, & NOMEN PAGE 2 OF 25 54 . 1 g 39.3 g 7 . 60 Na of mass Cl of mass = = 54 . 1 g 78.6 g 21.4 1 Na of mass Cl of mass = = 541 . 1 g 22.99 g 5.44 3 Na of mass Cl of mass = = Joseph Proust (1754 – 1826) Joseph Proust, a French Chemist, showed that “a given compound always contains the same proportion of elements by mass Law of Definite Proportion Example : Proportions of Sodium Chloride 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 A 58.44 g sample of sodium chloride contains 22.99 g of sodium and 35.44 g of chlorine John Dalton (1766 – 1844) Dalton reasoned that if elements were composed of tiny individual particles, a given compound should always contain the same combination of these atoms When two elements, (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 Law of Multiple Proportion Example : Oxides of Carbon Carbon combines with oxygen to form two different compounds Carbon Monoxide 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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Chapter 2 - Atomic Theory, Periodic Table, & Nomenclature (1)

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