Nuclear Chemistry

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Nuclear Chemistry
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• What is radioactivity?
• What are the 3 types of nuclear radiation?

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Nuclear Chemistry

• The study of changes that occur in the nucleus of
  an ATOM!!!
• Radioactivity - the process in which an unstable
  atomic nucleus emits charged particles and/or
  energy (also called nuclear decay)
• During "nuclear decay", an atom of one element
  can change into an atom of a different element.

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Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays




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Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element



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Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element
Involve only valence electrons May involve protons, neutrons, and electrons


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Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element
Involve only valence electrons May involve protons, neutrons, and electrons
Associated with small energy changes Associated with large energy changes

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Chemical vs. Nuclear Reactions
Chemical Reactions Nuclear Reactions
Occur when bonds are broken Occur when nuclei emit particles and/or rays
Atoms remain unchanged, although they may be rearranged Atoms often converted into atoms of another element
Involve only valence electrons May involve protons, neutrons, and electrons
Associated with small energy changes Associated with large energy changes
Reaction rate influenced by temperature, particle size, concentration, etc. Reaction rate is not influenced by temperature, particle size, concentration, etc.
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Radioactivity

• An unstable atomic nucleus emits a form of
  radiation (alpha, beta, or gamma) to become
  stable.
• In other words, the nucleus decays into a
  different atom.

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Radioactivity

• Alpha Particle Helium nucleus
• Beta Particle electron
• Gamma Ray high-energy photon

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Types of Nuclear Radiation

• Alpha particles
• Beta particles
• Gamma rays
• Nuclear Decay song

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Types of Nuclear Radiation

• Alpha particles - positively charged, made up of
  2 protons and 2 neutrons (same as a helium
  nucleus)
• Alpha decay - one product is ALWAYS a Helium
  nucleus 42 He
• The mass and atomic numbers of the reactant must
  equal the sum of the mass and atomic numbers of
  the products
• (ex) 22288Ra ? 42 He 218 86 Rn

Mass
Atomic
Look up element 86
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Beta Particles

• Beta particles electron emitted by an unstable
  nucleus, negatively charged particle
• Beta decay - one product is 0-1e (because of its
  negative charge, it is assigned an atomic number
  of -1)
• (ex) 146C ? 0-1e 147N
• (once again, the sums of mass number and atomic
  number of the products must equal the reactant)
• Once you find the atomic number, you look for the
  element on your periodic table!!!

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Alpha and Beta Decay Animation

• http//library.thinkquest.org/27954/dequ.htm

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Gamma Decay

• Gamma decay- penetrating ray of energy emitted by
  an unstable nucleus
• They have no mass and no charge
• Like X-rays and visible light, gamma rays travel
  at the speed of light
• During gamma decay, the atomic number and mass
  number of the atom remain the same, but the
  energy of the nucleus decreases
• X-rays are emitted by electrons outside the
  nucleus, while gamma rays are emitted by the
  nucleus.

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Decay Particles Penetrating Ability

• alpha particle
• Least penetrating (can be stopped by a sheet of
  paper or clothing)
• beta particle
• More penetrating that alpha (pass through paper,
  but stopped by a thin sheet of metal
• gamma ray
• Much more penetrating that alpha and beta (takes
  several centimeters of lead or several meters of
  concrete to stop gamma radiation)

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Effects of Nuclear Radiation

• Background radiation nuclear radiation that
  occurs naturally in the environment
• Examples radioisotopes in air, water, rocks,
  plants and animals
• Nuclear radiation can ionize atoms, so it can
  damage the cells and tissues of your body
• Bonds holding proteins and DNA may be broken
• Examples
• Alpha particles radon gas (can be inhaled and
  causes lung cancer)
• Beta particles can damage tissues more than alpha
  particles
• Gamma rays can expose all organs to ionization
  damage

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Detecting Nuclear Radiation

• Geiger counters
• Film badges

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Nuclear Chemistry on youtube

• http//www.youtube.com/watch?vaEBGE1Nm7vc

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Practice on Nuclear Decay

• Lets work on p. 1 of your Nuclear Chemistry
  packet!
• Homework p. 2 of packet

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Half-Life

• Amount of time it takes for one half of a sample
  of radioactive atoms to decay

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Medical Applications of Half-Life
Nuclide Half-Life Area of Body
I131 8.1 days Thyroid
Fe59 45.1 days Red Blood Cells
Sr87 2.8 hours Bones
Tc99 6.0 hours Heart
Na24 14.8 hours Circulatory System
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Half-Life Calculation 1

• You have 400 mg of a radioisotope with a
  half-life of 5 minutes. How much will be left
  after 30 minutes?

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To calculate

• Start with 400 mg.
• The half-life is 5 minutes, so how much will you
  have after 5 minutes?
• 200 mg
• Now, how much will you have at the 10 minute
  mark? (remember that after 5 minutes, you will
  half of what you started with at that particular
  time.)
• 100 mg
• Keep going until you have reached 30 minutes!
• You can also use fractionsyou try it!

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Half-Life Calculation 2

• Suppose you have a 100 mg sample of Au-191, which
  has a half-life of 3.4 hours. How much will
  remain after 10.2 hours?

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Half-Life Calculation 3

• Cobalt-60 is a radioactive isotope used in cancer
  treatment. Co-60 has a half-life of 5 years. If
  a hospital starts with a 1000 mg supply, how many
  mg will need to be purchased after 10 years to
  replenish the original supply?

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Half-Life Calculation 4

• A radioisotope has a half-life of 1 hour. If you
  began with a 100 g sample of the element at noon,
  how much remains at 3 PM? At 6 PM? At 10 PM?

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Half-Life Calculation 5

• How many half-lives have passed if 255 g of Co-60
  remain from a sample of 8160 g?

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Half-Life Calculation 6

• Suppose you have a sample containing 400 nuclei
  of a radioisotope. If only 25 nuclei remain
  after one hour, what is the half-life of the
  isotope?

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Half-Life Calculation 7

• If a radioactive element has diminished by 7/8 of
  its original amount in 30 seconds, what is its
  half-life?

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Answers to Half-Life Calculations

• Half-Life Calculation 1
• 6.25 mg
• Half-Life Calculation 2
• 12.5 mg
• Half-Life Calculation 3
• 750 mg

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Answers to Half-Life Calculations

• Half-Life Calculation 4
• 12.5 g, 1.5625 g, 0.09765625 g
• Half-Life Calculation 5
• 5 half-lives

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Answers to Half-Life Calculations

• Half-Life Calculation 6
• 15 minutes
• Half-Life Calculation 7
• 10 seconds

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Video on Fusion and Fission

• http//www.youtube.com/watch?v-Qliifidcuw
• Another one
• http//www.bbc.co.uk/schools/gcsebitesize/science/
  add_aqa/atoms_radiation/nuclearact.shtml

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Fission and Fusion

• Fission- splitting of atomic nuclei. Tons of
  energy produced from a small mass
• Fusion- combining atomic nuclei. Requires high
  temp, stars do this.

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Fission vs. Fusion

• Look at my Physical Science notes under nuclear
  chemistry

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Fission

• NOT a natural process
• Occurs as a result of neutron bombardment
• heavy nucleus (mass gt 200) splits into two
  similar sized pieces
• wide range of nuclei produced
• releases lots of energy b/c smaller nuclei more
  stable
• 235U and 239Pu most important

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Fission

• CONTROLLED
• Nuclear Power Plant
• UNCONTROLLED
• In reactor meltdown!
• Atomic bomb!

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Fission and Fusion
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Fusion

• nuclei fuse together
• for very light elements, stability increases with
  increasing mass
• energy released when two light nuclei combine to
  larger, more stable nucleus
• thermonuclear reaction - occurs only at very high
  temps
• lowest temperature required for fusion
  40,000,000 K
• occurs constantly in sun
• Plasma is an example (atoms have been stripped of
  their electrons)

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• Fusion
• Has it occurred on earth?
• Hydrogen bomb

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Section 10.4

• Comparing and Contrasting

a. is the splitting of a large nucleus into two
smaller fragments b. is widely used as an
alternative energy source
c. is the fusing of two small nuclei into one
larger nucleus d. is still being researched and
developed as an alternativeenergy source
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Fission vs. Fusion
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Radiation in our lives

• Background radiation
• cosmic rays in atmosphere
• radon from granite rock (lung cancer)
• Foods
• bananas, Brazil nuts
• Medical exposure
• Dental x-ray
• Cancer treatment (Cobalt-60)
• Detecting art forgeries
• Analyzing gunpowder residue
• Agricultural research, diagnose disease
• Smoke detectors (Americium-241)

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What do we do with Nuclear Waste?

• Bury it underground in a spot that is
  geologically stable!!
• SC has a nuclear waste site.

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Effects of Radiation Video Clips

• Gamma Radiation gone wrong
• Harmful effects of radiation
• Our radiation environment
• Chernobyl