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Chapter 1 Matter and Measurement 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 G[.]
General Chemistry Principles and Modern Applications Petrucci • Harwood • Herring 8th Edition Chapter 2: Atoms and the Atomic Theory Philip Dutton University of Windsor, Canada Prentice-Hall © 2002 Slide of 25 General Chemistry: Prentice-Hall â Contents ã Early chemical discoveries • Electrons and the Nuclear Atom • Chemical Elements • Atomic Masses • The Mole Slide of 25 General Chemistry: Prentice-Hall © Early Discoveries Lavoisier 1774 Law of conservation of mass Proust 1799 Law of constant composition Dalton 1803-1888 Atomic Theory Slide of 25 General Chemistry: Prentice-Hall © 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 Slide of 25 General Chemistry: Prentice-Hall © Consequences of Dalton’s theory Law of Definite Proportions: combinations of elements are in ratios of small whole numbers 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 Slide of 25 General Chemistry: Prentice-Hall © Behavior of charges Slide of 25 General Chemistry: Prentice-Hall © Cathode ray tube Slide of 25 General Chemistry: Prentice-Hall © Properties of cathode rays Electron m/e = -5.6857 x 10-9 g coulomb-1 Slide of 25 General Chemistry: Prentice-Hall © 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 Slide of 25 General Chemistry: Prentice-Hall © 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, He2+ β-particles are a stream of high speed electrons that originate in the nucleus Slide 10 of 25 General Chemistry: Prentice-Hall © The 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 protons 1919 James Chadwick neutrons 1932 Slide 13 of 25 General Chemistry: Prentice-Hall © Nuclear Structure Atomic Diameter 10-8 cm 1Å Particle Electron Proton Neutron Mass kg 9.109 x 10-31 1.673 x 10-27 1.675 x 10-27 Slide 14 of 25 Nuclear diameter 10-13 cm amu 0.000548 1.00073 1.00087 General Chemistry: Charge Coulombs –1.602 x 10-19 +1.602 x 10-19 (e) –1 +1 Prentice-Hall © Scale of Atoms The heaviest atom has a mass of only 4.8 x 10-22 g and a diameter of only x 10-10 m Useful units: amu (atomic mass unit) = 1.66054 x 10-24 kg pm (picometer) = x 10-12 m Å (Angstrom) = x 10-10 m = 100 pm = x 10-8 cm Biggest atom is 240 amu and is 50 Å across Typical C-C bond length 154 pm (1.54 Å) Molecular models are 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 Halogens Noble Gases Main Group Transition Metals Main Group Slide 18 of 25 Lanthanides and Actinides General Chemistry: Prentice-Hall â The Periodic Table ã ã ã ã 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 is impossible • We must be able to relate measured mass to numbers of atoms – buying nails by the pound – using atoms by the gram Slide 20 of 25 General Chemistry: Prentice-Hall © ... Prentice-Hall © The 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... amu and is 50 Å across Typical C-C bond length 154 pm (1.54 Å) Molecular models are Å /inch or about 0.4 Å /cm Slide 15 of 25 General Chemistry: Prentice-Hall © Isotopes, atomic numbers and mass... 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