## Episode 512: Nuclear equations

Lesson for 16-19

- Activity time 70 minutes
- Level Advanced

Now that your students are familiar with different types of radiation, you can look at the processes by which they are emitted.

Lesson 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: AZX

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.

Episode 512-1: Nuclide notation (Word, 36 KB)

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.

Episode 512-2: Decay processes (Word, 53 KB)

You could give examples of equations for the sources used in school and college labs.

α sources are americium-241, 24195Am

24195Am → 23793Np + 42He

β ^{-} sources are strontium-90, 9038Sr

9038Sr → 9039Np + 0-1e

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^{-} + n into the AZ notation:

10n → 11H + 0-1e

γ sources are cobalt-60, 6027Co. The γ radiation comes from the radioactive daughter 6028Ni of the β decay of the 6027Co.

The 6028Ni is formed in an excited state

and so almost immediately emits a γ ray. They are only emitted after an α or β decay, and all such γ 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

Episode 512-3: Practice with nuclear equations (Word, 66 KB)

The more unusual decay processes (positron emission, neutron emission, electron capture) could be included, and students challenged to write them as nuclear equations.