Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University1Chemistry 500: Chemistry in Modern LivingTopic 2: Protecting the Ozone LayerAtoms and LightChemistry in Context, 2nd Edition: Chapter 2, Pages 35-72Chemistry in Context, 3rd Edition: Chapter 2, Pages 45-92Outline Notes by Dr. Allen D. Hunter, YSU Department ofChemistry, 2000.Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University2Outline2A WHAT IS OZONE?............................................................................................................................................................32B WHAT IS THE STRUCTURE OF A ATOM?...........................................................................................................62C HOW DO WE KNOW MOLECULAR STRUCTURES?.....................................................................................112D HOW DO WE EXPLAIN MOLECULAR STRUCTURES?................................................................................132E WAVES OF LIGHT.........................................................................................................................................................172F WAVE/PARTICLE DUALITY.....................................................................................................................................202G THE OZONE SCREEN...................................................................................................................................................212H CFCS AND OZONE.........................................................................................................................................................26Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University32A What is Ozone?Ø Ozone FormationØ Produced from a variety of processes:Ø Photochemical Smog (Topic 1)Ø High Voltage Electrical DischargesMolecular Oxygen + Energy → Ozone3 O2 + Energy → 2 O3Ø Can be smelled at 10 ppbØ Arc WeldingØ Lightning StormsØ Laser PrintersØ Tesla CoilsChemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University4Ø AllotropesØ Different forms of the same elementØ They have different chemical structuresØ Hence different chemical propertiesØ Examples include:Ø Graphite (found in pencil lead) and Diamond (on rings)are different chemical forms of the element CarbonØ Molecular Oxygen and Ozone are different chemicalforms of the element OxygenChemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University5Ø The Allotropes of the Element OxygenØ Molecular Oxygen, O2Ø A Diatomic MoleculeØ Liquefies at -183 °CØ A light blue liquidØ OdorlessØ Ozone, O3Ø A Triatomic MoleculeØ Liquefies at -112 °CØ A dark blue liquidØ Used in water purification and pulp and paper bleachingØ Characteristic OdorØChemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University62B What is the Structure of a Atom?Ø Graphics from Text: Table 2.1, the Properties of Sub-AtomicParticlesØ Overview of Atoms and NucleiØ Diagram Not to Scale!Ø Nucleus actually tremendously smaller than the electroncloudØ The Electron Cloud includes both Core Electrons andValence ElectronsP+NNe-Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University7Ø Electrons, e-Ø Surround the NucleusØ Mass of 1/1838 AMUØ Charge of -1Ø Protons, P+Ø In the NucleusØ Mass of 1 AMUØ Charge of +1Ø Neutron, nØ In the NucleusØ Mass of 1 AMUØ Charge of 0Ø Neutron/Proton Ratio in Stable NucleiØ Due to balance of Strong Nuclear Force and ElectrostaticForceChemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University8Ø Evidence for this structureØ High Energy Diffraction / Collision ExperimentsØ Rubber Baggie model of nucleusØ IsotopesØ The same element (i.e., the same number of protons in thenucleus)Ø Different Mass due to different number of Neutrons in theNucleusØ Chemically Isotopes react extremely similarlyØ Examples:Ø 1H(Hydrogen), 2H (D, Deuterium), and 3H (T, Tritium)Ø 12C (common, 99%), 13C (rare, 1%, NMR), and 14C (veryrare, produced in upper atmosphere, radioactive)Ø 238U (non-radioactive) and 235U (radioactive)Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University9Ø The Periodic TableØ Use the Periodic Table to Evaluate the Number of e-, P+,and n in each isotopeØ Atomic Number ⇒ The number of Electrons and Protonsin the neutral atomØ Mass Number ⇒ The total number of Protons andNeutrons4He ⇒ # e- =# P+ =# n =40Ar ⇒ # e- =# P+ =# n =Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University10Ø Ask Students: For each of the following isotopes, give thetotal number of protons, neutrons, and electrons and then thenumber of valence electrons and core electrons.Ø Group Activity7Be ⇒ # e- =# P+ =# n =13C ⇒ # e- =# P+ =# n =19F ⇒ # e- =# P+ =# n =29Si ⇒ # e- =# P+ =# n =183W ⇒ # e- =# P+ =# n =Chemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University112C How Do We Know Molecular Structures?Ø How do we know molecular structures?Ø Analytical DataØ Spectroscopic MethodsØ Sporting MethodsØ Specific absorption of lightØ NMR = Nuclear Magnetic Resonance (cf. MRI, MagneticResonance Imaging)Ø Infra-Red (IR)Ø Ultra Violet-Visible (UV-Vis)Ø From the mid 1850s have know many molecular shapes butwere not able to explain them other than to say the atomswere connectedChemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University12Ø X-Ray Crystallography/DiffractionØ Non-Sporting MethodØ Single CrystalsØ HardwareØ Data CollectionØ Data AnalysisChemistry 500 Dr. Hunter’s Class Topic 2.2000, Dr. Allen D. Hunter, Department of Chemistry, Youngstown State University132D How Do We Explain Molecular Structures?Ø Theories change over time to better fit the experimental