Nuclear Chemistry

1
Nuclear Chemistry
2
Radioactivity

• Energy or particles emitted fr an unstable
  nucleus
• Light, heat, alpha, beta particles gamma rays

3
Types of Radiation

• 4
• Alpha(?)He nucleus 2He
• 0
• Beta (ß) an electron -1e high kinetic E
• Gamma(?) high penetrating energy
• ß ? can penetrate skin cause radiation
  sickness, cancer, or death
• Geiger counter device to detect environmental
  radiation wh triggers electrical signals th are
  counted

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Uses of Radiation

• Tracers- water, oil flow drugs
• Cancer treatment (gamma radiation)
• Radiation bombards cancer cells
• Carbon dating- determines relative age of items
  by measuring the ratio of stable and RA nuclei

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Nuclear Equations

• Sum of the mass s on the left right sides of
  the equation must be equal!
• Sum of the electrical charges on the left right
  sides of the equation must be equal!
• Decay RA particle is emitted (product)
• Bombardment or Capture RA particle is a
  reactant
• Other RA particles
• 1 1
• Proton 1H Neutron 0n
• 2 0
• Deutron 1H Neutrino (positron) e

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Nuclear Stability

• Of 1500 known isotopes, only 264 are stable
• Stability depends upon the neutronproton ratio
• Band of Stability (see graph) location of stable
  nuclei outside of this area, nuclei undergo
  spontaneous RA decay
• Region A too many neutrons turn a neutron
  into a proton by emitting a ß particle
• 1 1 0
• 0n -gt 1H -1-e ß-decay emission

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Nuclear Stability-cont.

• Region B too many protons
• Converts proton -gt neutron
• an e- is captured
• 59 0 59
• 28Ni -1e -gt 27Co
• Region C esp. heavy too many protons and
  neutrons
• Emits alpha particles
• 204 200 4
• 82Pb -gt 80Hg 2He
• All nuclei gt 82 are RA most undergo alpha
  emission

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Half Life

• The time it takes for half the RA elements in a
  sample to decay
• 100 -gt 50 -gt 25 -gt 12.5 -gt 6.25 -gt etc.
• Ea radioisotope has a unique half life fr
  milliseconds to 1000s of years
• Decay series - the successive transformations of
  a RA isotope until a stable isotope is formed

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Transmutation Reactions

• Transmutation - conversion of an atom of one
  element into an atom of another element
• Spontaneous/natural - Radioisotopes th decay
  14 14 6C -gt 7N
• Artificial - when high E particles ( protons,
  neutrons, alpha) bombard the nucleus
• 14 4 18
• 7N 2He -gt 9F
• Transuranium elements
• atomic gt 92
• Do not occur in nature
• Radioactive
• Synthesized by bombardment

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Nuclear Fission

• Splitting atoms nucleus broken into smaller
  nuclei by bombardment w/ neutrons
• Forms 2 unequal nuclei
• Emits neutrons lg amts of E
• Chain rxn self-propagating
• Released neutrons strike other nuclei they
  undergo fission releasing more E neutrons

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Nuclear Fission Reactors

• Core
• Fuel Rods
• Control Rods
• Moderators
• Coolant
• Steam Turbine
• Cooling Tower
• Nuclear E -gt Heat E -gt Mechanical E -gt Electrical
  E

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Nuclear Fission-cont

• Atomic Bomb - uncontrolled chain rxn
• Releases huge amts of E radiation
• Killing burning for miles
• Radiation w/ long half-lives
• Radiation sickness, cancer, death
• Requires a critical mass (min amt of material) to
  sustain the rxn

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Nuclear Waste

• Dangerous -emits radiation for 1000s of years
• Storage- currently at reactor sites
• Burial Yucca Mt ???
• Vitrification - sealed in glass

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Nuclear Fusion

• Sun releases E via
• 2 nuclei combine to produce a nucleus of heavier
  mass
• 1 0 4
• 4 1H 2 -1e -gt 2He Energy
• Only occurs when temp is gt 40,000,000 C

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Energy Mass in Nuclear Rxns

• When the total mass of reactants products in a
  nuclear rxn are compared, mass seems to
  disappear!!
• Nuclear Rxn
• E mc2 E energy (joules)
• m mass (kg)
• C speed of light
• 3.00x 108 m/s

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Energy Mass in Nuclear Rxns

• Loss of mass is proportional to E given off!
• Helps explain why a stable nucleus stays together
• Mass defect - the mass of a nucleus is slightly
  less than the sum of the individual masses of the
  protons neutrons th comprise it.

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Energy Mass in Nuclear Rxns

• Lower E a more stable nucleus
• Binding E the amt of E needed to break s
  nucleus into its individual protons neutrons
  (neucleons)

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Energy Mass in Nuclear Rxns

• BE can be calculated fr mass defect
• Mass of 1 mole of Hg-200
• 199.9244g
• Mass of 80 moles of protons
• 120 moles of neutrons
• 201.6228g

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Energy Mass in Nuclear Rxns

• 201.6228 g
• - 199.9244 g
• 1.6984 g
• Use this mass in E mc2 to find BE
• Most stable nuclei have a mass around 60

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Energy Mass in Nuclear Rxns

• Light nuclei give off E gain stability when
  they fuse together
• Heavy nuclei give off E when they break apart
  (fission)

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Radon Gas

• Naturally occurring decay product from U-238
• Emits alpha radiation
• Cause of lung cancer property concerns