Radioactive Decay

What is Radioactive Decay?

Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Radioactive Decay. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.

Check that you can explain Radioactive Decay in your own words and give one example from everyday life. If you can do that, you have understood the core idea.

Understanding Radioactive Decay explains how the physical world behaves, from sport and transport to electricity and medicine.

Radioactive Decay in detail

Radioactive decay is the random process in which an unstable nucleus emits radiation to become more stable. Alpha radiation is a helium nucleus (2 protons and 2 neutrons), strongly ionising but stopped by paper. Beta radiation is a fast electron, stopped by a few millimetres of aluminium. Gamma radiation is an electromagnetic wave, weakly ionising and reduced only by thick lead or concrete.

The decay is random, so we cannot predict when a given nucleus will decay, but the activity of a large sample follows predictable rules. Nuclear equations balance mass and atomic numbers. Radiation is detected with a Geiger-Müller tube.

How the interactive helps you understand Radioactive Decay

Watch the atom model in the interactive. Use any sliders or buttons it offers to change the values and see how the atom model responds.

Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Radioactive Decay.

Real-life uses and examples

• Use Radioactive Decay to make sense of a practical and its results.
• Answer “explain” questions by linking Radioactive Decay to a clear cause and effect.
• Predict what a ball, car or circuit will do with Radioactive Decay before you do the calculation.

Common mistakes to avoid

• Mixing up Radioactive Decay with a related quantity that has different units.
• Forgetting that some quantities, such as force or velocity, also have a direction.
• Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.