Nuclear Chemistry. Natural Radioactivity The spontaneous breakdown of atomic nuclei, accompanied by...
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Transcript of Nuclear Chemistry. Natural Radioactivity The spontaneous breakdown of atomic nuclei, accompanied by...
Nuclear Chemistry
Natural RadioactivityThe spontaneous breakdown of
atomic nuclei, accompanied by the release of some form of radiation
Transmutation: the conversion of one element to another by means of a nuclear changeTo detect Radioactivity one could use Geiger Counter
Types of Radioactive Emissions
All differ in mass, size and charge Reference Table O
Alpha Particle: 42
positive 2 chargehelium nucleusmass of 4amuEx: 226
88Ra 22286Rn + 4
2He
Beta Particle: 0-1
negative chargeacts like a high speed electronno mass
Example: 23592U 235
93Np + 0-1
Gamma Radiation (NOT a Particle) no chargeacts like a high speed x-ray but
with a lot more energyno mass
Positron Particle: 0+1
positive 1 chargeacts like positive electronsno mass
Particle Symbol Mass Charge Relative Penetrating Power
Alpha 42 4amu +2 Low
Beta 0-1 0 -1 Moderate
Gamma 00 0 0 High
Positron 0+1 0 +1 Moderate
Separation of Radioactive emissions by charge:
Positively Charged Plate Negatively Charged Plate
+ -
+ -
+ -
+ -
Half-Life The time it takes for half of the
atoms in a given sample of an element to decay.
Some selected half-lives are found on Table N
All reactions on Table N are Natural Transmutation
Formulas for half-life reactions are found on Table T
Artificial Radioactivity Artificial Transmutation: artificial
radioactivity produced by bombarding the nuclei of stable atoms with high energy particles, thereby producing radioactive atoms
Fission Reactions The splitting of an atomic nucleus
into two smaller nuclei by bombardment of a neutron (Nuclear Bomb). *Nuclear Reactors are fission reactors.
Example: 23592U + 1
0n 14256Ba + 191
36Kr + 3(1
0n) + Energy
Fusion Reactions A nuclear reaction in which two or
more light nuclei combine to form a single nucleus. Requires huge amounts of pressure and extremely high temperatures. Produces much more energy than fission. Occurs naturally on the sun. (H-bomb)
Example: 21H + 2
1H 42He + Energy
Uses of Radioactive Isotopes Lab: To trace chemical reactions.
Industry: Radiating food to preserve by killing bacteria, mold, insect eggs.
Medicine Must have relatively short half-
lives and be quickly eliminated from the body.
I-131 diagnosing and treating Thyroid conditions (half-life 8.07 days)
Co-60 emits large amounts of gamma radiation as it decays, these rays can be aimed at cancerous tumors (half-life 5.26 years)
Ra-226 used in treatment of certain cancers (half-life 1600 years)
Tc-99 used in diagnosis of brain tumors (half-life 2.13x105 years
GeologyFossils C-14 to C-12 ratio (while alive
they are in equal amounts, once an organism dies C-14 is no longer taken in).
Rocks U-238 to Pb-206 ratio (U-238 decays through a series of steps until it forms stable Pb-206. As time passes, the amount of U-238 decreases while the amount of Pb-206 increases).
Balancing Nuclear Equations Steps for Balancing:
Due to the Law of the Conservation of Matter, whatever is on the left side of the equation must also be on the right side of the equation.
Add the mass numbers on the left side of the equation, this MUST equal the total mass numbers of the right side of the equation.
Add the atomic numbers on the left side of the equation, this MUST equal the total atomic numbers on the right side of the equation.
Example: 3216S + 1
0n 11H + 32
15P