ci2.2 nuclear reactions
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Nuclear Processes
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In chemical reactions, electronsin atoms are responsible for
bonds forming and being
destroyed.
The identity of the atomsinvolved does not change
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This is not true for nuclearprocesses because;
These reactions involve the
protons and neutrons in the
nucleus
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There are two types of nuclearreaction
Fission and Fusion Reactions
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Fission Reactions
• Involve a nucleus collapsing to form a
smaller nucleus
• Usually involve atoms with large nucleii
such as the Lathanides and Actinides
• They produce , and emissions.
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Fusion Reactions
• These involve nucleii joining together to
make larger ones.
• These type of reactions are what go on
inside stars and provide the energy which
make them shine.
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The particle
• Consists of 2 protons
and 2 neutrons
• Is emitted from anucleus during radio
active decay
• Is the most destructive
radiation because it
ionises atoms it bumps
into
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An decay reaction
The Uranium atom U23892 decays by particle emission
U238
92He
4
2+ ?
234
90
What is represented by ?
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More decay reactions
The Thorium atom Th22790 decays by particle emission
Th227
90
Complete the equation
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More decay reactions
Th227
90He
4
2+ Ra
223
88
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More decay reactions
The Actinium atom Ac22589 decays by 3 particle emissions
Ac225
89
Complete the equation
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More decay reactions
Ac225
893He
4
2+ Bi
213
83
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Particle emissions
Particles are electrons but they do not come from the electron
shells which surround the nucleus – they come from the
nucleus itself.
The electron is emitted when a neutron becomes a proton.
N10 p1
1 0-1
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Particle emissions
The effect of Particle emission is to increase the proton count
by 1 whilst leaving the overall mass unchanged.
Th231
90
0
-1+ ?
What is ?
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Particle emissions
The effect of Particle emission is to increase the proton count
by 1 whilst leaving the overall mass unchanged.
Th231
90
0
-1+ Pa
Notice how particle emission raises the atomic number by 1
231
91
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Decay Series
When a radioactive nucleus such as U23892 decays it
often produces another radioactive isotope which
goes on to decay further.
We are going to construct a decay series on
graph paper for the element U238
92 to show howit eventually forms a stable isotope of lead
Pb20682
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GET A PIECE OF GRAPH
PAPER• Draw a vertical axis representing atomic
mass. It will need to run from 200 to 240
• Draw a horizontal axis representing atomicnumber. It will need to run from 78 to 93.
• Position the isotope U23892 on your graph
and mark it clearly.
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240
20078 93
Mass
Number
* U23892
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Plotting an decay
• The nucleus gives off an alpha particle first
to form a new nucleus
• Work out what the new nucleus is
• Find the nucleus on your graph and add it in
• Join the points with an arrow
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240
20078 93
Mass
Number
* U23892
Th23490 *
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Plotting a beta emission
• The Thorium next loses a Beta particle
• Work out what would be formed
• Add the nucleus onto your chart
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240
20078 93
Mass
Number
* U23892
Th23490 * * Pa234
91
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Building up the decay series
Continue to build up the series using the following
emissions. Each alpha emission is shown as a
diagonal to the left and each beta emission is ahorizontal line to the right.
If you are successful you should end up with Pb20682
Good Luck !
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Emission sequence (including the
first two example emissions)
1.
2.
3.
4.
5. 6.
7.
8.
9.
10.
11.
12. 13.
14.