Chemistry 1500: Chemistry in Modern Living. Topic 2: Protecting the Ozone Layer. Atoms and Light

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1 Chemistry 1500 Dr. unter s Class Topic 2 - Page 1 Chemistry 1500: Chemistry in Modern Living Topic 2: Protecting the Ozone Layer Atoms and Light Chemistry in Context, 2 nd Edition (1997): Chapter 2, Pages Chemistry in Context, 3 rd Edition (2000): Chapter 2, Pages Chemistry in Context, 4 th Edition (2003): Chapter 2, Pages Chemistry in Context, 5 th Edition (2006): Chapter 2, Pages The Figure, Table, & Problem numbers in these notes are taken from the 4 th edition of the text unless otherwise noted. Outline Notes by Dr. Allen D. unter, YSU Department of Chemistry, Graphics from Text: Figure 2.0, Antarctic Ozone ole as seen from space

2 Chemistry 1500 Dr. unter s Class Topic 2 - Page 2 Outline 2A WAT IS OZONE?...3 2B WAT IS TE STRUCTURE OF A ATOM?...6 2C OW DO WE KNOW MOLECULAR STRUCTURES? D OW DO WE EXPLAIN MOLECULAR STRUCTURES? E WAVES OF LIGT F WAVE/PARTICLE DUALITY G TE OZONE SCREEN TE BIOLOGICAL EFFECTS OF UV-LIGT AND SKIN CANCER I MOLECULAR REASONS FOR UV EFFECTS J CFCS AND OZONE K ALOCARBONS AND OZONE DESTRUCTION L RESPONSES TO OZONE LOSS...45

3 Chemistry 1500 Dr. unter s Class Topic 2 - Page 3 2A What is Ozone? Ozone Formation Produced from a variety of processes: Photochemical Smog (Topic 1) igh Voltage Electrical Discharges Molecular Oxygen + Energy Ozone 3 O 2 + Energy 2 O 3 Can be smelled at 10 ppb Arc Welding Lightning Storms Laser Printers Tesla Coils Pools

4 Chemistry 1500 Dr. unter s Class Topic 2 - Page 4 Allotropes Different forms of the same element They have different chemical structures ence different chemical properties Examples include: Graphite (found in pencil lead) and Diamond (on rings) are different chemical allotropic forms of the element Carbon Molecular Oxygen and Ozone are different allotropic forms of the element Oxygen

5 Chemistry 1500 Dr. unter s Class Topic 2 - Page 5 The Allotropes of the Element Oxygen Molecular Oxygen, O 2 A Diatomic Molecule Liquefies at -183 C A light blue liquid Odorless Ozone, O 3 A Triatomic Molecule Liquefies at -112 C A dark blue liquid Used in water purification and pulp and paper bleaching Characteristic Odor

6 Chemistry 1500 Dr. unter s Class Topic 2 - Page 6 2B What is the Structure of a Atom? Graphics from Text: Table 2.1, the Properties of Sub-Atomic Particles Overview of Atoms and Nuclei Diagram Not to Scale! Nucleus actually much much smaller than the electron cloud (1 Billion times)

7 Chemistry 1500 Dr. unter s Class Topic 2 - Page 7 The Electron Cloud includes both Core Electrons and Valence Electrons e - P + N N Electrons, e - Surround the Nucleus Mass of 1/1838 AMU Charge of -1 Protons, P + In the Nucleus Mass of 1 AMU Charge of +1

8 Chemistry 1500 Dr. unter s Class Topic 2 - Page 8 Neutron, n In the Nucleus Mass of 1 AMU Charge of 0 Neutron/Proton Ratio in Stable Nuclei Due to balance of Strong Nuclear Force and Electrostatic Force Evidence for this structure igh Energy Diffraction / Collision Experiments Rubber Baggie model of nucleus

Chemistry 1500 Dr. unter s Class Topic 2 - Page 9 Isotopes The same element (i.e., the same number of protons in the nucleus) Different Mass due to different number of Neutrons in the Nucleus

9 Chemistry 1500 Dr. unter s Class Topic 2 - Page 9 Isotopes The same element (i.e., the same number of protons in the nucleus) Different Mass due to different number of Neutrons in the Nucleus Chemically Isotopes react extremely similarly Examples: 1 (ydrogen), 2 (D, Deuterium), and 3 (T, Tritium) 12 C (common, 99%), 13 C (rare, 1%, NMR), and 14 C (very rare, produced in upper atmosphere, radioactive) 238 U (non-radioactive) and 235 U (radioactive) Graphics from Text: Table 2.3, Isotopes of ydrogen

10 Chemistry 1500 Dr. unter s Class Topic 2 - Page 10 The Periodic Table Use the Periodic Table to Evaluate the Number of e -, P +, and n in each isotope Atomic Number The number of Electrons and Protons in the neutral atom Mass Number The total number of Protons and Neutrons 4 e # e - = # P + = # n = 40 Ar # e - = # P + = # n =

11 Chemistry 1500 Dr. unter s Class Topic 2 - Page 11 Ask Students: For each of the following isotopes, give the total number of protons, neutrons, and electrons and then the number of valence electrons and core electrons. Group Activity 7 Be # e - = # P + = # n = 13 C # e - = # P + = # n = 19 F # e - = # P + = # n = 29 Si # e - = # P + = # n = 183 W # e - = # P + = # n =

12 Chemistry 1500 Dr. unter s Class Topic 2 - Page 12 2C ow Do We Know Molecular Structures? ow do we know molecular structures? Analytical Data Spectroscopic Methods Sporting Methods Specific absorption of light NMR = Nuclear Magnetic Resonance (cf. MRI, Magnetic Resonance Imaging) Infra-Red (IR) Ultra Violet-Visible (UV-Vis) From the mid 1850s have know many molecular shapes but were not able to explain them other than to say the atoms were connected

13 Chemistry 1500 Dr. unter s Class Topic 2 - Page 13 X-Ray Crystallography/Diffraction Non-Sporting Method Single Crystals ardware Data Collection Data Analysis

14 Chemistry 1500 Dr. unter s Class Topic 2 - Page 14 2D ow Do We Explain Molecular Structures? Theories change over time to better fit the experimental data A Theory should explain all current data and predict future results Lewis Dot Structures Lewis developed this theory to explain know molecular structures, reactivity data, and emerging ideas like electricity and radioactivity Bonds were due to shared pairs of electrons Lone Pairs of Valence Electrons remain on many atoms Only the Valence Electrons Contribute to bonding This accounts for the fact that elements underneath one another on the periodic table react similarly

15 Chemistry 1500 Dr. unter s Class Topic 2 - Page 15 Rigorous Method of Determining Lewis Dot Structures Count the total number of valence electrons for the molecules Distribute them around the atoms such that each atom gets as close to a complete Octet as possible An Octet is 8 for most elements but 2 for ydrogen and elium Some elements will allow / settle for greater or lesser than 8 electrons but we won t see these in Chem. 500 C C C C S

16 Chemistry 1500 Dr. unter s Class Topic 2 - Page 16 Quick and Dirty Method for getting Lewis Structures An oversimplification that can break down but works well for most Organic Compounds Bond Lengths Bond Angles one bond and no lone pairs F, Cl, Br, and I one bond and three lone pairs O, S, Se, and Te two bonds and two lone pairs N, P, As, and Sb three bonds and one lone pair C, Si, Sn, and Ge four bonds and no lone pairs C C C C S

17 Chemistry 1500 Dr. unter s Class Topic 2 - Page 17 Ask Students: For each of the following molecules, draw the correct Lewis Dot Structures including all Bonds and Lone Pairs Group Activity O C C C C C Cl O C C C O C Cl Se C C O N C I

18 Chemistry 1500 Dr. unter s Class Topic 2 - Page 18 2E Waves of Light Graphics from Text: Figure 2.2, Two Different Waves The relationship between Frequency, Wavelength, and Amplitude for Electromagnetic Waves

19 Chemistry 1500 Dr. unter s Class Topic 2 - Page 19 Electromagnetic Spectrum Wavelength of Electromagnetic Waves Long wavelengths correspond to low energy waves Is inversely related to the Frequency of Electromagnetic Waves Wavelength = Speed of Light / Frequency λ = C / ν C = Speed of Light = 3 x 10 8 m/sec

20 Chemistry 1500 Dr. unter s Class Topic 2 - Page 20 Frequency of Electromagnetic Waves igh frequency corresponds to high energy waves Is inversely related to the Wavelength of Electromagnetic Waves Frequency = Speed of Light / Wavelength ν = C / λ Amplitude of Electromagnetic Waves Is related to the intensity of the wave

21 Chemistry 1500 Dr. unter s Class Topic 2 - Page 21 Graphics from Text: Figure 2.3, Rainbows and The Electromagnetic Spectrum The relationship between frequency and wavelength for various types of electromagnetic radiation

22 Chemistry 1500 Dr. unter s Class Topic 2 - Page 22 Graphics from Text: Figure 2.4 & Figure 2.5, Rainbows and The Electromagnetic Spectrum

23 Chemistry 1500 Dr. unter s Class Topic 2 - Page 23 Graphics from Text: Figure 2.6, Solar Radiation Profile The distribution of electromagnetic radiation of various energies produced by the sun as they appear from just above the earth s atmosphere Note: the Overall Profile (Black Body Radiation) The Spikes and Valleys (Specific Absorptions by Materials between the eye and the sun. Ask Students: As the temperature of the object changes, how will the shape of Figure 2.3 change? Group Activity

24 Chemistry 1500 Dr. unter s Class Topic 2 - Page 24 2F Wave/Particle Duality Light is Wave Like Evidence includes Diffraction I.e., light bends Light is Particle Like Evidence includes Photoelectric Effect I.e., there is a threshold energy for light to cause its effects Wave / Particle Duality Light has Both Wave and Particle Like Properties Plank s Relationship E = h ν h is Plank s Constant ( 6.63 x joule seconds) igher Frequency igher Energy Lower Frequency Lower Energy Wave Packet Model

25 Chemistry 1500 Dr. unter s Class Topic 2 - Page 25 2G The Ozone Screen Graphics from Text: Figure 2.8, Atmospheric Sunscreen The atmosphere (and especially the Stratospheric Ozone Layer) acts as sunscreen to select out which wavelengths of light reach the earth s surface

26 Chemistry 1500 Dr. unter s Class Topic 2 - Page 26 Graphics from Text: Figure 2.9, Atmosphere s effect on solar radiation reaching the earth s surface The atmosphere screens us from high energy UV light reaching the surface

27 Chemistry 1500 Dr. unter s Class Topic 2 - Page 27 Graphics from Text: Figure 2.5 in 3 rd Edition, Ozone s Absorption of Ultra-Violet Radiation Ozone absorbs high energy UV light

28 Chemistry 1500 Dr. unter s Class Topic 2 - Page 28 2 The Biological Effects of UV-Light and Skin Cancer Graphics from Text: Figure 2.10, DNA Sensitivity of UV Light

29 Chemistry 1500 Dr. unter s Class Topic 2 - Page 29 Graphics from Text: Figure 2.11, Map of US Skin Cancer Risks

30 Chemistry 1500 Dr. unter s Class Topic 2 - Page 30 Graphics from Text: Figure 2.12, Skin Cancer Incidence Risk Changing with Time in US

31 Chemistry 1500 Dr. unter s Class Topic 2 - Page 31 Graphics from Text: Table 2.5, Types and Characteristics of UV-Light

32 Chemistry 1500 Dr. unter s Class Topic 2 - Page 32 2I Molecular reasons for UV effects Graphics from Text: Figure 2.7, Effects of Ultraviolet Light on Chemical Bonds Molecular Oxygen, O 2, absorbs the highest energy UV light UV light with λ less than about 242 nm O 2 + photon 2 O Ozone, O 3, absorbs the medium energy UV light UV light with λ less than about 320 nm (i.e., lower energy)

33 Chemistry 1500 Dr. unter s Class Topic 2 - Page 33 Ozone has a typical lifetime of about one or two hundred seconds Ozone has a weaker O-O bond than molecular oxygen and this bond is therefore broken by lower energy photons Ozone Cycle O 3 + photon O 2 + O Ozone generation in the atmosphere O + O (formation of ozone)

34 Chemistry 1500 Dr. unter s Class Topic 2 - Page 34 Graphics from Text: Figure 2.15, Ozone concentration profile of the atmosphere Ozone concentrations are highest in the part of the stratosphere referred to as the Ozone Layer Graphics from Text: Figure 2.14, The Chapman Cycle of Ozone in the Atmosphere

35 Chemistry 1500 Dr. unter s Class Topic 2 - Page 35 Ozone Destruction Free Radicals!!! Radicals are molecules or atoms with one or more unpaired electrons This makes them extremely reactive and they can catalyze reaction such as Ozone destruction 2 O + energy. +. O. + O 3. O + O 2. O + O. + O 2. + O 3 +. O + O. O + O O 2 Net Reaction: O + O 3 2 O 2

36 Chemistry 1500 Dr. unter s Class Topic 2 - Page 36 Ozone Loss Arctic and Antarctic Sensitivity Caused by extreme cold tiny crystals whose surfaces are involved in Ozone destruction Note: Noise levels in data Graphics from Text: Figure 2.17, Average Ozone loss on the earth

37 Chemistry 1500 Dr. unter s Class Topic 2 - Page 37 Graphics from Text: Figure 2.18, Average Ozone loss on the earth A few percent in continental US

38 Chemistry 1500 Dr. unter s Class Topic 2 - Page 38 Graphics from Text: Figure 2.16, Ozone loss in Antarctica About 50% in the high Antarctic Graphics from Text, Figure 2.0: Intro Page of Chapter, 2001 Antarctic Stratospheric Ozone ole

39 Chemistry 1500 Dr. unter s Class Topic 2 - Page 39 2J CFCs and Ozone alocarbons Compounds containing only C, Cl, F, Br, and Are typically expensive but safe non-toxic, non-flammable, non-reactive, and quite volatile Used as refrigerants, blowing agents, propellants, cleaning agents for computer parts, dry cleaning fluids, decaffeination

40 Chemistry 1500 Dr. unter s Class Topic 2 - Page 40 Classes of alocarbons CFCs are Chlorofluorocarbons These are chemicals that contain only C, Cl, and F Examples include: CFCl 3 (Freon 11) and CF 2 Cl 2 (Freon 12) Graphics from Text: Table 2.6, CFC-11 & CFC-12 alons contain C, Br, and F and/or Cl Examples include: C 3 Br, CF 2 Br 2 and CClBr 3 Used for fire extinguishers Chlorocarbons contain C, Cl, and Examples include CCl 3 -C 3 and C 2 Cl 2

41 Chemistry 1500 Dr. unter s Class Topic 2 - Page 41 2K alocarbons and Ozone Destruction They are generally safe at ground level, why are they dangerous in the Stratosphere? They are so stable that unlike most chemicals they escape destruction in the decade or so it takes them to make it to the Stratosphere This means that they can transfer Chlorine and Bromine atoms here much better than other chemicals In the Stratosphere, these Cl and Br containing compounds produce Cl. and Br. radicals which catalyze Ozone destruction Bromine radicals are much less concentrated but are much more destructive The man made examples of halocarbons are typically more stable than the natural ones and therefore typically make it to the Stratosphere better

42 Chemistry 1500 Dr. unter s Class Topic 2 - Page 42 Reactions that destroy Ozone CF 2 Cl 2 + energy CF 2 Cl. +. Cl Cl. + O 3. OCl + O 2. OCl + O Cl. + O 2 Cl. + O 3 +. OCl + O. OCl + O 2 +. Cl + O 2 Net Reaction: O + O 3 2 O 2 Note: this reaction is very similar to that for Ozone destruction by hydrogen radicals, it is just much faster and thus more efficient The analogous reaction with bromine radicals is even faster and more efficient

43 Chemistry 1500 Dr. unter s Class Topic 2 - Page 43 Graphics from Text: Figure 2.20, Chlorine - Ozone Correlations

44 Chemistry 1500 Dr. unter s Class Topic 2 - Page 44 Solutions? Many now in place or being put into effect Montreal Treaty Cost Concerns Safety Concerns Technology Concerns ydrochlorofluorocarbons Supercritical CO 2 Greenhouse gasses

45 Chemistry 1500 Dr. unter s Class Topic 2 - Page 45 2L Responses to Ozone Loss Montreal Protocol Graphics from Text: Figure 2.23, Reported Global CFC Production CFC Replacement Graphics from Text: Table 2.7, CFC-22 & CFC-141b

46 Chemistry 1500 Dr. unter s Class Topic 2 - Page 46 Index of Vocabulary and Major Topics 1 12 C C... 9, C W F U U Si Ar e Be A Allotropes... 4, 5 allotropic forms... 4 Amplitude... 18, 20 Analytical Data Antarctic Antarctic Stratospheric Ozone ole Arc Welding... 3 Arctic Ask Students... 11, 17, 23 atmosphere... 9 Atmosphere s effect on solar radiation Atmospheric Sunscreen... 25, 31 Atomic Number Atoms... 6 Average Ozone loss on the earth B Black Body Radiation blowing agents bond Bond Angles Bond Lengths Bonds C C C, Si, Sn, and Ge four bonds and no lone pairs Cancer Incidence Carbon... 4 catalyze CCl 3 -C CClBr CF 2 Br CF 2 Cl CFC CFC Production CFC CFC CFCl CFCs and Ozone C 2 Cl C 3 Br Chapman Cycle Charge... 7, 8 Chlorine - Ozone Correlations Chlorocarbons Chlorofluorocarbon cleaning agents for computer parts Core Electrons... 7 Cost Concerns D D... 9 decaffeination Deuterium... 9 Diamond... 4 Diatomic Molecule... 5

47 Chemistry 1500 Dr. unter s Class Topic 2 - Page 47 Diffraction DNA Sensitivity of UV Light dry cleaning fluids E e , 10 E = h ν Electrical Discharges... 3 electricity Electromagnetic Spectrum... 19, 21, 22 Electromagnetic Waves... 18, 19 Electron Cloud... 7 Electrons... 7, 10 Electrostatic Force... 8 element... 4, 9 Energy... 3 expensive but safe...see experimental data F F, Cl, Br, and I one bond and three lone pairs Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure , 27 Figure Figure Figure Figure Free Radicals Freon Frequency... 18, 20, 24 G Graphics from Text... 1, 6, 9, 18, 21, 22, 23, 25, 26, 27, 28, 29, 30, 31, 32, 34, 36, 37, 38, 41, 44, 46 Graphite... 4 Greenhouse gasses Group Activity... 11, 17, 23 alocarbons... 40, 41 alocarbons and Ozone Destruction alons CFC-141b CFC ow Do We Explain Molecular Structures ow Do We Know Molecular Structures. 12 ydrochlorofluorocarbons ydrogen... 9 I in Stable Nuclei... 8 Infra-Red intensity IR isotope Isotopes... 9 Isotopes of ydrogen... 9 L Laser Printers... 3 Lewis Lewis Dot Structures lifetime Light has Both Wave and Particle Like Properties Light is Particle Like Light is Wave Like Lightning... 3 Liquefies... 5 lone pairs Lone Pairs M Magnetic Resonance Imaging... 12

48 Chemistry 1500 Dr. unter s Class Topic 2 - Page 48 Mass... 7, 8, 9 Mass Number Molecular Oxygen... 3, 4, 5, 32 molecular shapes molecular structures Montreal Treaty MRI N n... 8, 10 N, P, As, and Sb three bonds and one lone pair Net Reaction neutral atom Neutron... 8 Neutron/Proton Ratio... 8 Neutrons NMR... 9, 12 Noise levels in data non-flammable non-reactive non-toxic Nuclear Magnetic Resonance Nuclei... 6 Nucleus... 6, 7 O O, S, Se, and Te two bonds and two lone pairs O , 5, 32 O , 5, 32 Octet Odorless... 5 Organic Compounds Oxygen... 4 Ozone... 3, 4, 5, 27, 32, 33 Ozone concentration profile of the atmosphere Ozone Cycle Ozone Destruction Ozone generation Ozone Loss Ozone loss in Antarctica P P , 10 pencil lead... 4 periodic table Periodic Table Photochemical Smog... 3 Photoelectric Effect photon Plank s Constant Plank s Relationship Pools... 3 propellants properties... 4 Protons... 7, 10 pulp and paper bleaching... 5 Q Quick and Dirty Method for getting Lewis Structures R Radicals radioactive... 9 radioactivity Rainbows... 21, 22 Reactions that destroy Ozone refrigerants Rigorous Method of Determining Lewis Dot Structures Rubber Baggie model of nucleus... 8 S Safety Concerns shared pairs of electrons Single Crystals Skin Cancer Risks Solar Radiation Profile Spectroscopic Methods Speed of Light Sporting Methods Stratosphere Stratospheric Ozone Layer Strong Nuclear Force... 8 structures... 4 Sub-Atomic Particles... 6

49 Chemistry 1500 Dr. unter s Class Topic 2 - Page 49 Sunscreen Supercritical CO T T... 9 Table Table Table Table Table Technology Concerns Tesla Coils... 3 The Ozone Screen... 25, 28 Theory threshold energy Triatomic Molecule... 5 Tritium... 9 U Ultra Violet-Visible Ultra-Violet Radiation unpaired electrons UV light... 27, 32 UV-Vis V Valence Electrons... 7, 14 volatile W water purification... 5 Wave / Particle Duality Wave Motion Wave Packet Model Wave/Particle Duality Wavelength... 18, 19 Waves of Light What is Ozone... 3 What is the Structure of a Atom... 6 X X-Ray Crystallography/Diffraction λ λ... 19, 20, 32 ν ν... 19, 20

Chapter 2 Protecting the Ozone Layer. The Ozone Hole

Chapter 2 Protecting the Ozone Layer. The Ozone Hole Today (Tues 2/24) Newspaper Articles: Ciara Rodwell and Melissa Regan Intro to Ozone, Ozone Hole, & Chapter 2 Light, matter, and human health! Laboratory: Experiment 4 You design investigation Start Ozone