Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 1 of 25 Chapter 2: Atoms and the Atomic Theory Philip Dutton University of Windsor, Canada Prentice-Hall © 2002 General Chemistry Principles and Modern Applications Petrucci • Harwood • Herring 8 th Edition Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 2 of 25 Contents • Early chemical discoveries • Electrons and the Nuclear Atom • Chemical Elements • Atomic Masses • The Mole Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 3 of 25 Early Discoveries Lavoisier 1774 Law of conservation of mass Proust 1799 Law of constant composition Dalton 1803-1888 Atomic Theory Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 4 of 25 Dalton’s Atomic Theory Each element is composed of small particles called atoms. Atoms are neither created nor destroyed in chemical reactions. All atoms of a given element are identical Compounds are formed when atoms of more than one element combine Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 5 of 25 Consequences of Dalton’s theory In forming carbon monoxide, 1.33 g of oxygen combines with 1.0 g of carbon. In the formation of hydrogen peroxide 2.66 g of oxygen combines with 1.0 g of hydrogen. Law of Definite Proportions: combinations of elements are in ratios of small whole numbers. Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 6 of 25 Behavior of charges Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 7 of 25 Cathode ray tube Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 8 of 25 Properties of cathode rays Electron m/e = -5.6857 x 10 -9 g coulomb -1 Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 9 of 25 Charge on the electron From 1906-1914 Robert Millikan showed ionized oil drops can be balanced against the pull of gravity by an electric field. The charge is an integral multiple of the electronic charge, e. Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 10 of 25 Radioactivity Radioactivity is the spontaneous emission of radiation from a substance. X-rays and γ-rays are high-energy light. α-particles are a stream of helium nuclei, He 2+ . β-particles are a stream of high speed electrons that originate in the nucleus. [...]... (1.54 Å) Molecular models are 1 Å /inch or about 0.4 Å /cm Slide 15 of 25 General Chemistry: Prentice-Hall © Isotopes, atomic numbers and mass numbers To represent a particular atom we use the symbolism: A= mass number Slide 16 of 25 Z = atomic number General Chemistry: Prentice-Hall © Measuring atomic masses Slide 17 of 25 General Chemistry: Prentice-Hall © Alkali Metals The Periodic table Alkaline Earths... nuclear atom Rutherford protons 1919 James Chadwick neutrons 1932 Slide 13 of 25 General Chemistry: Prentice-Hall © Nuclear Structure Atomic Diameter 10-8 cm 1Å ParticleMass Electron Proton Neutron Nuclear diameter 10-13 cm Charge kg 9.109 x 10-31 1.673 x 10-27 1.675 x 10-27 Slide 14 of 25 amu 0.000548 1.00073 1.00087 General Chemistry: Coulombs –1.602 x 10-19 +1.602 x 10-19 0 Prentice-Hall © (e) –1 +1... nuclear atom Geiger and Rutherford 1909 Slide 11 of 25 General Chemistry: Prentice-Hall © The α-particle experiment Most of the mass and all of the positive charge is concentrated in a small region called the nucleus There are as many electrons outside the nucleus as there are units of positive charge on the nucleus Slide 12 of 25 General Chemistry: Prentice-Hall © The nuclear atom Rutherford... Transition Metals Main Group Slide 18 of 25 Lanthanides and Actinides General Chemistry: Prentice-Hall © The Periodic Table • • • • Read atomic masses Read the ions formed by main group elements Read the electron configuration Learn trends in physical and chemical properties We will discuss these in detail in Chapter 10 Slide 19 of 25 General Chemistry: Prentice-Hall © The Mole • Physically counting atoms... atoms – buying nails by the pound – using atoms by the gram Slide 20 of 25 General Chemistry: Prentice-Hall © Avogadro’s number The mole is an amount of substance that contains the same number of elementary entities as there are carbon-12 atoms in exactly 12 g of carbon-12 NA = 6.02214199 x 1023 mol-1 Slide 21 of 25 General Chemistry: Prentice-Hall © Molar Mass • The molar mass, M, is the mass of one... 0.012% atoms 40K atoms 40K = (9.49 x 10-3 mol K) x (6.022 x 1023 atoms K/mol K) x (1.2 x 10-4 40K/K) Slide 24 of 25 = 6.9 x 1017 40K atoms Prentice-Hall © General Chemistry: Chapter 2 Questions 3, 4, 11, 22, 33, 51, 55, 63, 83 Slide 25 of 25 General Chemistry: Prentice-Hall © ... atoms do you ingest by drinking one cup of whole milk containing 371 mg of K? Want atoms of 40K, need atoms of K, Want atoms of K, need moles of K, Want moles of K, need mass and M(K) Slide 23 of 25 General Chemistry: Prentice-Hall © Convert strategy to plan and plan into action Convert mass of K(mg K) into moles of K (mol K) mK(mg) x (1g/1000mg) mK (g) x 1/MK (mol/g) nK(mol) nK = (371 mg K) x (10-3... mol-1 Slide 21 of 25 General Chemistry: Prentice-Hall © Molar Mass • The molar mass, M, is the mass of one mole of a substance M (g/mol 12C) = A (g/atom 12C) x NA (atoms 12C /mol 12C) Slide 22 of 25 General Chemistry: Prentice-Hall © Example 2-9 Combining Several Factors in a Calculation—Molar Mass, the Avogadro Constant, Percent Abundance Potassium-40 is one of the few naturally occurring radioactive . numbers. Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 6 of 25 Behavior of charges Prentice-Hall © 2002 General Chemistry: Chapter 2 Slide 7. 2002 General Chemistry: Chapter 2 Slide 8 of 25 Properties of cathode rays Electron m/e = -5.6857 x 10 -9 g coulomb -1 Prentice-Hall © 2002 General Chemistry: