Name: ________________________
Date: _____
Balancing Nuclear Reactions
Decay Review
• Describe the changes that occur from alpha, beta (+/-), and neutron decay.
Alpha Æ
Beta (+) Æ
Beta (-) Æ
Neutron Æ
Balancing Nuclear Reactions
• In the reactants (starting materials – on the left side of an equation) and products (final
products – on the right side of an equation)
o _____________________________________ must balance and
o _____________________________________ must balance
• Use a particle or isotope from Table O to fill in the missing protons and neutrons
Balancing Nuclear Equations
U + n→
235
92
1
0
Balancing Nuclear Equations
226
88
Ra → α +
4
2
Ba + Kr + 3 n
142
56
91
36
1
0
Balancing Nuclear Equations
U + n → I +2 n+
235
92
1
0
139
53
1
0
Transmutations
• __________________________________________________________________
__________________________________________________________________.
•
_______________ transmutation = radioactive decay of unstable elements
–
•
Ex:
_______________ transmutation = a change brought about by bombarding the nucleus
of a stable atom with high energy particles, such as neutrons, protons, alpha particles.
•
Neutrons can easily penetrate the nucleus of an atom because they have no charge.
•
Alpha particles and protons are repelled by the nucleus but with great quantities of
energy they can penetrate the nucleus. They can gain this energy in particle accelerators.
•
How can YOU tell the difference between a natural and artificial transmutation?
–
The natural transmutation will have _______ reactant (a radioactive nucleus).
–
The artificial transmutation will have ________ reactants (a fast moving particle
and a target nucleus).
FISSION REACTIONS
• __________________________________________________________________
__________________________________________________________________.
•
ENORMOUS amounts of _____________ are released!
•
Each neutron produced will bombard another uranium-238.
•
The generation of nuclear power is an example of Artificial transmutation.
Nuclear Fission & POWER
• Currently about 103 nuclear power plants in the U.S. and about 435 worldwide.
•
17% of the world’s energy comes from nuclear.
•
The Fission Reaction of Uranium-235
Chain reaction
• Chain reaction = one in which the material that starts the reaction is also one of the
products and can start a new reaction.
•
Fission reactions produce the energy used in _______________________.
•
These are ________________ fission reactions (the number of neutrons produced is
controlled).
•
This fuel __________ than fossil fuels and there is __________ produced.
•
BUT because the fuels and products of fission are _______________, they pose a
health hazard to people who may accidentally be exposed.
Nuclear Reactors- fission reactions occur
• In nuclear reactors the heat generated by the reaction is used to produce steam that
turns a turbine connected to a generator.
What is done with the products of fission (nuclear energy)?
• Solid radioactive wastes (strontonium-90 and cesium-137) are sealed in containers and
_______________ in isolated areas.
•
Low-level radioactive wastes are ________________ into the atmosphere.
•
Gaseous radioactive wastes (radon-222,krypton-85,nitrogen-16) are stored until they
___________ to safe levels and released into the atmosphere.
FUSION REACTIONS
• Two or more light nuclei ________ to form a single nucleus of greater mass.
• __________________________________________________________!
• The sun’s energy is believed to be the result of four hydrogen nuclei combining at very
high temperatures to make a helium nucleus.
• In order to get the nuclei to fuse, _______________________________
___________________________ are needed.
• We can _________ achieve Fusion reactions on Earth
– Excessive heat cannot be contained
– Attempts at “cold” fusion have FAILED.
– “Hot” fusion is difficult to contain.
Fusion
• The mass of the products is less than the mass of the reactants, because
_________________________________________________________
(Famous equation: E = mc2)
Review: Nuclear Fission and Fusion
• Fusion: _________________ two light nuclei to form a heavier, more stable nucleus.
• Fission: _______________ a heavy nucleus into two nuclei with smaller mass numbers.
•
•
There are two big problems that scientists and engineers face when trying to create a
fusion reaction.
– (1) Fusion can only occur at very high temperatures, such as 100 million degrees.
– (2) The fused atoms must be held together long enough for the reaction to
complete.
Commercial applications of fusion, for both space and everyday power sources will provide
us with a safe, clean, inexhaustible energy source.
USES AND DANGERS OF RADIOISOTOPES
• 1. Radioactive _________________
• 2. Chemical ___________________
• 3. _________________ applications
1. Radioactive Dating
• Radioactive isotopes can be used to date previously living materials or non-living
materials.
• Carbon-14 = used to date ________________
• Uranium-238 = decays to Pb-206 used to date ____________
• Radioactive C-14 is formed in the upper atmosphere by nuclear reactions initiated by
neutrons in cosmic radiation
14
N + 1on ---> 14C + 1H
• The C-14 is oxidized to CO2, which circulates through the biosphere.
• When a plant dies, the C-14 is not replenished.
• But the C-14 continues to decay with t1/2 = 5730 years.
• Activity of a sample can be used to date the sample.
2. Chemical Tracers
• Tracer = any radioisotope used to follow the ____ of a material in a system.
• Radioisotopes behave the same as stable isotopes. Reactions in living systems can be
traced using carbon-14.
3. Medical applications
• Radioisotopes with very short half-lives are administered to ____________ for
diagnostic purposes.
• Examples:
– Technetium-99 is used to determine the location of brain and other cancerous
___________.
– Iodine-131 is used to diagnose __________ problems.
– Radium and cobalt-60 are used in __________ therapy.
– Intense gamma radiation can be used to _______________ on foods (Cobalt-60
and cesium-137 can destroy anthrax)
• Food Irradiation
– Food can be irradiated with gamma rays from 60Co or 137Cs.
– Irradiated milk has a shelf life of 3 mo. without refrigeration.
– USDA has approved irradiation of meats and eggs.