Unit 3, part c

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Unit 3, part c

• Atomic Theory

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EQ

• How does the instability of an atom relate to its
  nuclear structure?

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GPS

• SC3. Students will use the modern atomic theory
  to explain the characteristics of atoms.
• a. Discriminate between the relative size,
  charge, and position of protons, neutrons, and
  electrons in the atom.
• c. Explain the relationship of the proton number
  to the elements identity.
• d. Explain the relationship of isotopes to the
  relative abundance of atoms of a particular
  element.

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Atomic number is the _____ number and it tells
how many ______.

• a. bottom, protons neutrons
• b. bottom, protons
• c. top, protons neutrons
• d. top, protons

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An isotope is an atom with the same number of
_______ but a different number of ________.

1. neutrons, protons
2. protons, neutrons
3. protons, electrons
4. electrons, protons

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Review

• Calculate the atomic mass
• 1H 12
• 2H 48
• 3H 40

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Nuclear reactions involve changes in an atoms
___________ while chemical reactions involve
changes with _________________.

1. nucleus, electrons
2. electrons, nucleus

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Radioactivity

• Chemical reaction involves only an atoms
  electrons the nucleus remains unchanged
• Nuclear reaction involves a change in an atoms
  nucleus (p or n0) represented in an nuclear
  equation (22688Ra ? 22286Rn 42?) .
• Nuclear Decay the transformation of an element
  into a different isotope of the same element or
  change into an entirely different element.
• Radioactivity is when unstable substances
  spontaneously emit radiation the rays and
  particles emitted are radiation
• 4 types of radiation alpha, beta, gamma,
  neutron emission

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The reason why atoms undergo radioactive decay is
to become unstable.

1. True
2. False

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Radioactivity

• When there are too many protons vs neutrons, the
  positive charges will repel each other causing
  the atom to be unstable
• Unstable ? radioactive decay ? stable
• ? ? radioactive decay ? ?

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The following show the correct order of strength
of radiation from strongest to weakest.

1. alpha, gamma, beta
2. alpha, beta, gamma
3. gamma, beta, alpha
4. gamma, alpha, beta

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Nuclear Reactions

• Alpha Radiation
• a 2 protons 2 neutrons
• Can be stopped with paper (tissue paper)
• 241 237 4
• 95 93 2

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Nuclear Reactions

• Beta Radiation
• ß particle
• negative charge
• Fast moving electron
• Electron particle made from neutron decay
• Can be stopped with foil (think aluminum foil)
• 14 14 0
• 6 7 -1

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Nuclear Reactions

• Gamma Radiation
• Energy (not matter) released from breaking bonds
  in nucleus
• Occurs with a or ß radiation
• Can be stopped with lead or concrete
• 238 234 4 0
• 92 90 2 0

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Nuclear Chemistry
Type Symbol Power Shielding
Alpha particle- ? made of 2 p 2 n. 4? 4 He 2 2 low Paper clothing
Beta particle-?/e electron made from neutron decay 0? 0e -1 -1 medium Metal foil
Gamma ray no charge no mass not matter- just EM radiation 0 ? 0 high Lead concrete
neutron emission 1 n 0 High unstable Travels farther- blocked by 15 cm Pb block.
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• Conversion of an atom of one element to an atom
  of another element is called transmutation.

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Half Life-

• Time it takes for ½ of radioisotopes nuclei to
  decay
• Each element has a unique half life
• Polonium-214 163.7 microseconds
• Radon-222 3.8 days
• Carbon-14 5730 years
• Uranium-238 4,460,000,000 years

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Half Life- uses

• Used for radioactive dating
• Medical procedures (diagnose treat disease),
  trace particle through system (DNA, fertilizers)

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Half Life

• Either memorize formula OR
• Amount remaining initial amount x (½ )n
• Where n is the number of half lives that passed
• Amount remaining initial amount x (1/2)t/T
• t elapsed time, T duration of half life (must
  be in same units!)
• Draw Pictures/ diagram

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Half-life t1/2

Half-lives X Amount left (grams)
0 1/2 100 of grams
1 1/2 1/2
2 1/2 1/4
3 1/2 1/8
4 1/2 1/16
5 1/2 1/32
6 1/2 1/64
Etc. 1/2 etc.
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Practice Half-life t1/2

• 2.00 g of N-13 emits B radiation decays to O-13
  with a ½ life of 10 minutes.
• How long is 3 half-lives?
• 10 min x 3 t1/2 30 min.
• How many g of the isotope are left after 3 half
  lives? 2.00 g x ½ x ½ x ½ 0.25 g left
• or since 3 t1/2 1/8, 2.00 g x 1/8 0.25
  g

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Practice T1/2

• The half-life of cobalt-60 is 5.3 years. How
  much of a 20.0 g sample will remain after 21.2
  years?
• 21.2/ 5.3 4 t1/2
• 4 t1/2 is 1/16
• So, 20.0 g

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• The carbon-14 in a sample of bone has ¼ of its
  original amount. How old is the bone? (Carbon-14
  has a half-life of 5730 years)

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• 2. Only 1/8th of the original dose of radon-222
  remains in a test subject. How long ago was the
  radon introduced into the test subjects body?
  (Radon-222 has a half-life of 3.8 days)

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• 3. Barium-139 has a half-life of 43 minutes. How
  many hours will it take to degrade to 1/32nd of
  its original amount?

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• 4. Polonium-211 has a half-life of 3.2 days.
  How long will it take to degrade to 1/128th of
  its original amount?

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• 5. Cobalt - 60 is used to detect leaks in water
  lines. It has a half life of 38 hours. It can not
  be detected by the sensors after it reaches 1/32
  of its original amount. How many days do
  engineers have to test the water lines before the
  Cobalt 60 is undetectable?

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Gas prices keep going up, up, and up.
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• The problem now is that cars have to be plug in
  everyday

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Nuclear Fission

• Process of one atom breaking down into smaller
  atoms
• splitting nucleus into smaller fragments by
  bombarding it with neutrons
• Chain reaction, high energy, use control rods to
  slow reaction
• Uses bombs, nuclear power
• http//lectureonline.cl.msu.edu/mmp/applist/chain
  /chain.htm

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• Biggest problem with nuclear power is the nuclear
  waste
• Currently, the depleted uranium is stored
  underground in Yuma, Arizona.

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Nuclear Fusion

• Fusion is the process of combining 2 smaller
  atoms into one larger atom w/ a grater mass
• Produces 10 times more energy than fission
• Lots of E, process too hot to control,
• sun
• No nuclear waste! ?

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Recap

• Radiation Penetration
• Alpha a
• Beta ß
• Gamma ?
• Nuclear power
• Biggest problem?
• Waste disposal or nuclear meltdown?

• Fission
• Fusion