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CHM 107
2.1 Ozone
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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.
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 O2(g) g 2 O3(g)
Lightning can serve as the Energy (E)
O3 more reactive than O2, ozone can bleach
Ozone O3
Oxygen
O2
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http://eospso.gsfc.nasa.gov/
Earth Observing System
Monitors air quality using satellites
2.2 Atomic Structure
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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.
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Atomic mass = sum of pro + neu
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Atomic number = # pro
◦ Why not electrons?
◦ How can you find # of neutrons?
◦ # protons defines the element, it is how elements are
numbered in the Periodic Table
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Atoms are neutral meaning no charge
◦ Thus # pro must equal # of what?
In an atom, # pro = # e-
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
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The outermost electrons of an atom are the ones
that bond with other atoms. = Valence electrons
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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
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How many protons, neutrons, electrons, are
in:
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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.
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We write single atoms like 12C and 13C 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 15N? What about 3H?
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 12.011 a.m.u. that you see in the table
Atom
20F
1H
4He
23Mg
#pro
#ele
#neu
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2.3 Molecules
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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 H2, O2 and N2
◦ Single covalent bond = 2 electrons shared
◦ Double = 4 electrons shared
◦ Triple = 6 electrons shared
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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?
– line
 4 bonded electrons is two lines or =
 6 bonded electrons is three lines or =
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2 bonded electrons can be drawn by
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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.
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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 2.
2.4 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?
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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?
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2.6 Oxygen Ozone screen
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UV-A = 320 – 400 nm long, they all reach
Earth’s surface, “black light”
UV-B = 280-320 nm long, they are absorbed
by ozone molecules, O3
UV-C = 200-280 nm long, they are absorbed
by oxygen molecules, O2
Which one is the most dangerous? Why?
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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.
2.7 Effects of UV radiation
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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
◦ 2/3rd of Australians get skin cancer! (1600
deaths per year)
◦ Should wear spf 15 and sunglasses
◦ UV-B causes retinal damage, cataracts
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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
1981
1987
1993
1999
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2.8 Ozone Destruction – where is it going?
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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
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CFC = carbon, fluorine, and chlorine
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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.
◦ CCl3F is Freon-11
◦ CCl2F2 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. + O3 g ClO. + O2
 ClO. g Cl. and O
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So the Cl can repeat step one again, and again…
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http://www.youtube.com/watch?v=qUfVM
ogIdr8
2.10 Why over Antarctica?
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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
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Amazing example of world wide cooperation.
1978 North America bans CFC’s in spray cans.
United Nations adopts a plan in 1977
1987 the Montreal Protocol is written – a plan to
phase almost all CFC’s out by 2000. Signed by
189 countries now.
Even asthma inhalers changed in 2008.
Will take to mid century to reach 1980 ozone
levels
China leader in illegal CFC trade (second only to
their illegal drug trade! )
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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.
2.12 CFC Replacements
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HCFC’s can be used until 2030
◦ H for what element?
◦ Example: HCClF2 – only one Cl and persists 20 years
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HFC’s are being phased in now, no Cl atoms
◦ Hydrogen, fluorine and carbon only
◦ Example: CH2F2 and C2HF5 often blended, nontoxic,
nonflammable called R-410A. New A/C’s being built to
use this replacement.
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Let’s draw these to see the difference
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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
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