Ionising Radiation
Quantum and Nuclear

A stockpile of nuclei during decay

Teaching Guidance for 14-16 Supporting Physics Teaching

Piles of nuclei: changing but not being removed

It's quite helpful to get students to visualise radioactive decay in terms of a stockpile of atoms containing nuclei. The word stockpile fosters an image of a pile of atoms. This remains constant, but the nuclei inside the atoms are transmuted, and so the atoms are transmuted. During radioactive decay, the number of atoms stays constant but the number of nuclei of any sort can vary with time. If you're focusing on a single-step decay then the stockpile of nuclei you start off with will gradually get depleted (stock levels of that kind of nucleus go down: stock levels of all kinds of nuclei are constant).

Teacher Tip: Some things (the numbers of particular kinds of nuclei) change; some stay the same (the total number of nuclei). Apples do change to oranges, but here the number of pieces of fruit stay the same.

This is, of course, very different from fission and fusion, where nuclei split or join. The number of atoms will therefore change.

Ionising Radiation
is used in analyses relating to Radioactive dating
can be analysed using the quantity Half-Life Decay Constant Activity
features in Medical Physics
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