Chapter 2 - Protecting the Ozone Layer Flashcards
What is the formula for ozone?
energy + 3 O2 –> 2 O3
What is ozone?
an allotropic form of energy (different form of same element, differ in structure and properties)
What are the characteristics of oxygen?
- colorless gas
- odorless
- light blue liquid
- boiling point: -193 degrees (gas –> liquid)
- reactive (supports combustion)
What are the characteristics of ozone?
- colorless gas
- definite odor
- dark blue liquid
- boiling point: -112 degrees (gas –> liquid)
- very reactive
Where is ozone found?
- majority in stratosphere
- also found in troposphere (ozone increases from pollution)
Good vs. Bad Ozone
Good: in upper atmosphere ozone blocks UV rays
-90% of ozone is in “ozone layer” (9.3-18.6 miles above ground)
Bad: lower atmosphere ozone produces photochemical smog
-10% of ozone here at 1.5 miles above ground and lower
What is the structure of an atom?
nucleus: center, dense, contains protons/neutrons
electrons: orbit nucleus
What are the elementary particles of atoms?
- Electrons
- negative charge
- orbit atom nucleus
- very tiny (compared to protons/neutrons) - Protons
- positive charge
- in nucleus
- 2000x size of electron - Neutrons
- no charge
- in nucleus
- 2000x electron size (but heavier than protons)
What are the protons and neutrons called?
nuclons
What is a neutral atom?
when the # of protons = # of electrons
What determines an element’s identity?
depends on # of protons (atomic #, above symbol)
What are ions?
when an element has a different number of electrons
-atomic particle with a charge
–>ex. 17 protons and 18 electrons = +1 charge
17 protons and 16 electrons = -1 charge
What are isotopes?
when an element has a different number of neutrons
–>ex. 6p, 6n, 6e = Carbon-12
6p, 7n, 6e = Carbon-13
6p, 8n, 6e = Carbon-14
What are neutrons?
- uncharged
- add mass to atoms
- change # of neutrons –> same kind of atom physically, reacts the same, same mass, may affect stability (heavier = less stability –> isotopes
26
F
Iron
55.85
atomic number
atomic symbol
atomic name
atomic mass (not mass #)
What does changing the number of particles do?
- protons –> identity of atom
- neutrons –> isotopes
- electrons –> ions
What are valence electrons?
larger atoms - many electron layers
- shells/layers
- valence = outermost electrons
- involved in reactions
- determine chemical properties
- “want” same # of valence electrons as nearest Group 8A element (noble gases-stable/unreactive)
- Group # tells number of valence electrons
What are molecules?
when 2 or more atoms are bound
What is a covalent bond?
when atoms share electrons
- 2 electrons shared between 2 atoms = single covalent bond
- 4 electrons shared between 2 atoms = double covalent bond
- 6 electrons shared between 2 atoms = triple covalent bond
What are Lewis Structures?
Show the electron pairing between atoms
What is the octet rule?
atoms prefer to have 8 valence electrons (shared + unshared)
–> exceptions are H or He (which have 2 electrons max)
Steps to drawing Lewis Structures
- Find # of valence electrons
- Write the skeletal structure
- Put electrons around the “outside” atoms until octet
- Put any remaining electrons on central atom
- Assign formula charge
- If needed, use lone pairs from “outside atoms” to make multiple bonds giving central atoms an octet
- -> must satisfy octet over neutral charges
Oxygen vs. Ozone
see notes
Why is there a reactivity difference between oxygen and ozone?
oxygen has a double bond, hard to break = less reactive
ozone has a single bond, easier to break = more reactive
What is the relationship between wavelength and frequency?
inverse relationship
-longer wavelength (waves per second) = lower frequency
What is the speed of light?
3 x 10^8 m/s
What are the units of frequency?
sec^-1: inverse seconds, cycles per second
Hz: Hertz
symbol: v
Wavelength
lambda
-different wavelength = different kind of light
What is the equation for energy?
E = H x v
What is the equation for frequency?
v = c / wavelength
What is the relation between energy, frequency, and wavelength?
increased energy = increased frequency = shorter wavelength
What are the three types of light that come from the sun?
- visible: most intense
- IR: most abundant (53%)
- UV: most damaging (higher freq/energy)
What are the characteristics of light?
- lights is a particle
- light has no mass
- light moves in waves
What is the unit of energy?
joules (J)
What is Planck’s constant?
6.63 x 10^-34 Jxs
What happens when light hits matter?
- IR- molecules vibrate, matter heats up
- Visible- excites electrons, chemical reactions can occur (photosynthesis)
- UV- knock electrons off –> charged particles
- higher frequency UV- break covalent bond (disrupt biological processes, damage tissues, cancer)
UV-A light
320-400nm
lowest energy
least damaging, most abundant on earth
UV-B light
280-320nm
more energy than UV-A
more damaging than UV-A, mostly absorbed by ozone in stratosphere
UV-C light
200-280nm
almost completely absorbed by oxygen and ozone in stratosphere
most damaging
Chapman Cycle
on ppt
What is the difference in absorption in oxygen vs. ozone?
oxygen: 200-242nm
ozone: 200-320nm
Why does ozone absorb a broader range of light?
it is more reactive
“bond and a half” weaker than a double bond in oxygen
What are the biological effects of UV radiation?
- consequences depend on: energy of radiation, sensitivity to light, and time of exposure
- melanoma: linked with intensity and latitude of which you live
What is our cause for concern of UV radiation?
- short wavelengths = massive DNA cleavage
- 280nm is 100,000 times more damaging than 320nm
- ozone concentration is dropping
What are natural causes of ozone fluctuation?
- seasonal variation of UV intensity
- sunspot activity cycles
- wind: cloud cover
- random fluctuations
What causes ozone destruction naturally?
- water
- NO
What are Chlorofluorocarbons?
- Cl + F + C
- man made gases
- unreactive (nontoxic, nonflammable, cheap)
What are halons?
- C + Br + Cl or F
- no H
Inert CFCs
.
What are replacements for CFCs?
- HCFC (hydrochlorofluorocarbons): break down faster ut still have Cl
- HFC (hydrofluorocarbons): no Cl or Br, retool equipment, greenhouse gases
- HFO (hydrofluoroolefins): C=C, break down fast, replace HFC’s
- CO2: greenhouse gases, compression, $$$
- Propane: nontoxic but flammable, cheap?
