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Episode 512: Nuclear equations
Now that your students are familiar with different types of radiation, you can look at the processes by which they are emitted.
Summary
Discussion: Nuclide notation and N-Z plot. (10 minutes)
Student Questions: Practice with notation. (10 minutes)
Worked Examples: Equations for alpha, beta and gamma decay. (20 minutes)
Student Questions: Practice with nuclear equations. (30 minutes)
Discussion:
Nuclide notation
Revise nuclide notation:
Discuss how A = mass or nucleon number, Z = charge or atomic number and N = neutron number are related (A = Z + N).
Discuss isotopes (common examples: H, D and T, U-235 and U-238, C-14 and C-12).
Set the task of finding out the name for nuclides having the same A but different Z (isobars), and the same N but different Z (isotones).
Show an N-Z plot (Segrè plot).
Student questions:
Practice with notation
Set some simple questions involving nuclide notation.
Grid showing change in A and Z with different emissions
Worked examples:
Equations for alpha, beta and gamma decay
Nuclear decay processes can be represented by nuclear equations. The word equation implies that the two sides of the equation must ‘balance’ in some way.
You could give examples of equations for the sources used in school and college labs.
a sources are americium-241,
b- sources are strontium-90,
The underlying process is:
n –> p + e- + n
Here, n is an antineutrino. Your specification may require you to explain why this is needed to balance the equation.
You can translate n –> p + e- into the AZ notation:
g sources are cobalt-60
The g radiation comes from the radioactive daughter
of the b decay of the. The
is formed in an ‘excited state’ and so almost immediately loses the energy by emitting a g ray. They are only emitted after an a or b decay, and all such g rays have a well-defined energy. (So a cobalt-60 source which is a pure gamma emitter must be designed so that betas are not emitted. How? – (by encasing in metal which is thick enough to absorb the betas but which still allows gammas to escape.)
Student questions:
Practice with nuclear equations
TAP 512-3: Practice with nuclear equations
The more unusual decay processes (positron emission, neutron emission, electron capture) could be included, and students challenged to write them as nuclear equations.
Download Word version of Episode 512 (178 KB)
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