Nuclear chemistry

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Nuclear chemistry
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Subatomic Particles

• Protons- plus charge
• In the nucleus
• Neutrons- neutral
• Electrons - negative charge
• Outside the nucleus

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• http//www.teachersdomain.org/resources/phy03/sci/
  phys/energy/radsource/index.html
• http//www.teachersdomain.org/resources/tdc02/sci/
  life/evo/radiodating/index.html
• http//www.teachersdomain.org/resources/phy03/sci/
  phys/matter/date/index.html
• http//www.teachersdomain.org/resources/phy03/sci/
  phys/matter/threemile2/index.html

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Stability of Nuclei

• http//www.eas.asu.edu/holbert/eee460/decay.html
• Ratio of neutrons to protons determines stability
  belt of stability
• Ratio of nuclei with atomic numbers greater than
  83 makes those nuclei unstable (radioactive,
  radioisotope)
• Unstable nucleus decays forming products that are
  more stable emits radiation

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Radiation

• Radiation comes from the nucleus of an atom.
• Unstable nucleus emits a particle or energy ?
  alpha
• ? gamma
• ? beta

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Types of Radiation

• Alpha particle (?)
• helium nucleus

paper
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• Beta particle (?-)
• electron

1-
lead

• Positron (?)
• positron

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concrete

• Gamma (?)
• high-energy photon

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Alpha Emission
Numbers must balance!!
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Beta Emission
Numbers must balance!!
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Positron Emission
Numbers must balance!!
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Balancing Nuclear Equations

• 1) Use Table N to determine decay mode
• 2) In the reactants and products
• Atomic and mass numbers must balance
• 3) A new element will be formed
• according to the new atomic number

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DECAY MODE
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Learning Check 1

• What forms when carbon -14 decays?

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Solution 1

• What forms when carbon -14 decays?
• 14C ? 0 ? 14 N
• 6 -1 7

Worksheet Balancing nuclear equations
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Half-Life of a Radioisotope

• The time for the radiation level to fall (decay)
  to one-half its initial value
• decay curve
• 8 mg 4 mg 2 mg 1 mg

initial
1 half-life
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3
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http//www.eas.asu.edu/holbert/eee460/decay.html
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Examples of Half-Life

• Isotope Half life
• C-15 2.4 sec
• Ra-224 3.6 days
• Ra-223 12 days
• I-125 60 days
• C-14 5700 years
• U-235 710 000 000 years

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HALF- LIFE
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Learning Check 2

• How many half lives will it take for 50 grams
  of 99 Tc to decay to 6.25 g?
• ½ life amount time

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Solution 2

• How many half lives will it take for 50 grams of
  99 Tc to decay to 6.25 g? 3 half lives
• ½ life amount
  time
• 0 50 0
• 1 25 2.13 x 105
• 2 12.5 2 (2.13 x 105)
• 3 6.25 3 (2.13 x 105)

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• ½ life amount time

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Transmutation

• One element becomes another.

Natural Alpha Beta Gamma Positron
Artificial Fission Fusion
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Nuclear Fission

• Fission
• larger unstable nuclei break up into smaller
  more stable nuclei release of neutrons causes a
  chain reaction and energy release
• 235U 1n 139Ba 94Kr 3 1n
• 92 0 56
  36 0

Energy
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Fission
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Nuclear Power

• Fission Reactors

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Nuclear Power

• Fission Reactors

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Nuclear Fusion

• Fusion
• small nuclei combine
• 2H 3H 4He 1n
• 1 1
  2 0
• Occurs in the sun and other stars, hydrogen bomb

Energy
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Nuclear Power

• Fusion Reactors (not yet sustainable)

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Nuclear Power

• Fusion Reactors (not yet sustainable)

National Spherical Torus Experiment
Tokamak Fusion Test Reactor Princeton University
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Fission vs. Fusion
FISSION
FUSION

• 235U is limited
• danger of meltdown
• toxic waste
• thermal pollution

• fuel is abundant
• no danger of meltdown
• no toxic waste
• not yet sustainable

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Nuclear Weapons

• Atomic Bomb
• chemical explosion is used to form a critical
  mass of 235U or 239Pu
• fission develops into an uncontrolled chain
  reaction
• Hydrogen Bomb
• chemical explosion ? fission ? fusion
• fusion increases the fission rate
• more powerful than the atomic bomb

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Learning Check 3

• Indicate if each of the following are
• Fission (2) fusion
• Nucleus splits
• Large amounts of energy released
• Small nuclei form larger nuclei
• Hydrogen nuclei react

Energy
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Solution 3

• Indicate if each of the following are
• Fission (2) fusion
• 1 Nucleus splits
• 1 2 Large amounts of energy released
• 2 Small nuclei form larger nuclei
• 2 Hydrogen nuclei react

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Nuclear Chemistry Uses

• Dating
• dating previously living materials (Carbon-14)
• dating rocks and other geological formations
  (Uranium-238)

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Nuclear Chemistry Uses

• Medical Application
• Radiation Treatment
• larger doses are used to kill cancerous cells
  in targeted organs (Cobalt-60)
• Radioisotope Tracers
• (absorbed by specific organs and used to
  diagnose diseases)
• Iodine-131 detection and treatment of thyroid
  conditions
• Technetium-99 detects presence of tumors

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Nuclear Chemistry Uses

• Food Irradiation
• ? radiation is used to kill bacteria (Co-60 and
  Cs-137)
• Consumer Products
• ionizing smoke detectors - 241Am

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Nuclear Chemistry Uses

• Radioactive Tracers
• (tracers follow the path of a material in a
  system)
• Map the path of carbon in metabolic processes
• (Carbon-14)
• study plant growth, photosynthesis
  (Phosphorus-31)

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Nuclear power plant.
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Diagram for the tentative plan for deep
underground isolation of nuclear waste.