2.1 Ozone. Ozone O 3. Oxygen O 2 1/30/2015 CHM 107

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1 CHM Ozone In the stratosphere way up high Protects Earth from solar radiation There is a hole in the ozone layer above Antarctica Do we care? Why? Energy + 3 O 2 (g) g 2 O 3 (g) Lightning can serve as the Energy (E) O 3 more reactive than O 2, ozone can bleach Act before the bad affects on humans are significant or irreversible. We did this regarding ozone depletion. The world came together to solve the ozone depletion problem and solved this issue through legislation. Ozone O 3 Oxygen O 2 1

2 Earth Observing System Monitors air quality using satellites 2.2 Atomic Structure Nucleus atom s center where protons and neutrons are located Orbitals areas around the nucleus where electrons go round and round 3 particles Proton is +1 charge, mass of 1 a.m.u. Neutron is 0 charge, mass of 1 a.m.u. Electron is 1 charge, mass of ~0 a.m.u. In an atom, # pro = # e - Atomic mass = sum of pro + neu Why not electrons? Atomic number = # pro How can you find # of neutrons? # protons defines the element, it is how elements are numbered in the Periodic Table Atoms are neutral meaning no charge Thus # pro must equal # of what? The first level contains 1 orbital, an s orbital and 2 electrons live there max The second level contains 2 orbitals, an s and p orbitals, and 2+6 = 8 electrons max live there There are more levels that get more complicated Let s practice drawing some small atoms on the board The outermost electrons of an atom are the ones that bond with other atoms. = Valence electrons Column 1 has one outer electron Column 2 has two outer electrons And so forth Column 8 has 8 outer electrons and is stable, these are called the Noble Gases and they don t make bonds with other atoms (except He has 2 electrons) All other atoms want to be like the Noble Gases, so they make bonds to get to 8 outer electrons (octet rule) except H which only wants 2 electrons 2

3 How many protons, neutrons, electrons, are in: Carbon 13 Oxygen 16 Sodium 23 Chlorine 35 Note the number after the dash is the mass number. A single atom has a whole number mass (pro + neu) since you can t have part of a proton or neutron. Can t have ½ proton. BUT the Periodic Table has the mass with decimal places. Why? The table has the average mass of all the atoms in the world for that element, and the number of neutrons varies. Carbon is number 6 so 6 protons. Most carbon atoms have a mass of 12. That means how many neutrons? A few carbon atoms have a mass of 13. That means how many neutrons? So the number of neutrons may vary, but protons stays the same for an element. Carbon-12 and carbon-13 are called isotopes of each other. The average of all the carbon-12 and carbon-13 atoms is a.m.u. that you see in the table We write single atoms like 12 C and 13 C which is the same as carbon-12 and carbon-13. The 12 and 13 is the MASS number. The atomic number we get from the table = 6. (6 protons) Atoms of the same element with different # neu are called isotopes. How many protons, neutrons and electrons are in an atom of 15 N? What about 3 H? Atom 20 F 1 H 4 He 23 Mg #pro #ele #neu 3

4 2.3 Molecules Molecule = 2 or more atoms bonded together. If they are the same it is called a. If they are different it is called a. Nonmetal atoms can bond by SHARING electrons = covalent bonding. Drawing Lewis dot structures of H 2, O 2 and N 2 Single covalent bond = 2 electrons shared Double = 4 electrons shared Triple = 6 electrons shared 2 bonded electrons can be drawn by line 4 bonded electrons is two lines or = 6 bonded electrons is three lines or = Nonbonded electrons are drawn by dots or : They are always paired so called lone pairs You must be able to answer questions about the structures if they are given. I don t expect you to draw the structures yourself. How many lone pairs in each structure? Which molecule has single bonds? Double? Triple? How many bonded electrons are in each? Nonbonded? Which atom does not obey the octet rule? As in which atom does not have 8 electrons around itself? Your instructor will draw several dot structures on the board. Judge each structure and decide whether or not it follows the octet rule, which states that all atoms want to have 8 outer electrons except H which only wants Wavelength As wavelength gets longer, energy gets As wavelength gets shorter, energy gets On the previous slide which wave has the lower energy? The longer wavelength? 4

5 Frequency (n) = how many waves pass per second As wavelenth increases, n. As wavelenth decreases, n. Which waves travel faster? Which waves are longest? Which waves are shortest? Which waves cause heat? Which waves can we see? Which waves travel fastest? How many waves are hitting you right now? Are you melting? 53% is IR 39% is visible 8% is UV Light can be thought of as waves, but also as particles called photons. UV photons are energetic enough to knock electrons out of some atoms leaving them as charged ions. Some UV photons can even break bonds. 2.6 Oxygen Ozone screen UV-A = nm long, they all reach Earth s surface, black light UV-B = nm long, they are absorbed by ozone molecules, O 3 UV-C = nm long, they are absorbed by oxygen molecules, O 2 Which one is the most dangerous? Why? 2.7 Effects of UV radiation Which is not likely to reach us? Ozone has decreased in the stratosphere for the last 30 years. Skin cancer has increased cause more UV-B! 1 million cases in the US every year 2/3 rd of Australians get skin cancer! (1600 deaths per year) Should wear spf 15 and sunglasses UV-B causes retinal damage, cataracts 5

6 Fish eggs near Antarctica are being damaged which causes problems in the food chain on up to humans. There is an ozone hole above Antarctica

7 2.8 Ozone Destruction where is it going? Natural variations in ozone by season, but a hole is not natural. The hole has been as large as North America in 1994 and 2006! Ozone is naturally destroyed by OH and NO free radicals (radical has one unpaired electron) But the past 30 years something unnatural has been killing ozone molecules. What??? Anyone know? Remember what Rush said? 2.9 Evil Chlorofluorocarbons CFC = carbon, fluorine, and chlorine Nobel Prize in Chemistry 1995 for discovering CFC s cause the ozone hole (winners = Rowland, Molina, Crutzen) CFC s = manmade compounds with Cl, F, C Well known CFC s are Freon-11 and 12. They are refrigerants used in AC units and refrigerators. Also in aerosol cans. CCl 3 F is Freon-11 CCl 2 F 2 is Freon-12 Let s draw their structures and answer questions: how many single bonds? How many lone pairs? This is a bummer to industry since CFC s are cheap, plentiful, work really well, odorless, nontoxic and nonflammable. They don t want to stop making them. How do CFC s kill ozone? They break off a chlorine atom which kills ozone. One Cl atom can kill 100,000 ozone molecules alone!!! Holy crap! Cl. + O 3 g ClO. + O 2 ClO. g Cl. and O So the Cl can repeat step one again, and again 7

8 ogidr Why over Antarctica? Air patterns at that level in the stratosphere carry the CFC molecules south The South pole is coldest spot on Earth and polar clouds form with tiny ice crystals. Reactions occur on the ice surface to create chlorine radicals during sunlight winter days More UV-B rays get through the hole which is why southern Chile and Australia have much higher rates of skin cancer than anywhere else in the world 2.11 Global Response Amazing example of world wide cooperation North America bans CFC s in spray cans. United Nations adopts a plan in the Montreal Protocol is written a plan to phase almost all CFC s out by Signed by 189 countries now. Even asthma inhalers changed in Will take to mid century to reach 1980 ozone levels China leader in illegal CFC trade (second only to their illegal drug trade! ) 8

9 CFC chemicals persist in the atomosphere for up to 120 years. Although we no longer produce CFC s, they still exist above Antarctica. Will take until around 2050 for the ozone layer to recover to 1980 levels CFC Replacements HCFC s can be used until 2030 H for what element? Example: HCClF 2 only one Cl and persists 20 years HFC s are being phased in now, no Cl atoms Hydrogen, fluorine and carbon only Example: CH 2 F 2 and C 2 HF 5 often blended, nontoxic, nonflammable called R-410A. New A/C s being built to use this replacement. Let s draw these to see the difference Seasonal Energy Efficiency Rating 6 is a very common rating for older units produced prior to the 1990's 16 is very common for newer high-efficiency units 21 is awesome now 9

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