S4.11.2 For the adult
Alpha, beta and gamma
Radiation comes in three kinds. What are they, and how can we tell them apart?
What this chapter teaches
Alpha is a helium nucleus, beta is a fast electron from the nucleus and gamma is an electromagnetic wave. They differ in charge, ionising power and what stops them. Nuclear equations balance mass numbers and atomic numbers: alpha lowers them by 4 and 2, beta raises the atomic number by 1, and gamma changes neither.
Three questions to ask
There is no one right wording. Listen for the idea.
- Which is stopped by paper, and which is reduced only by thick lead?
- What changes in the nucleus when it gives out a beta particle?
- A nucleus decays by alpha emission. What happens to its mass number and atomic number?
After the chapter, the learner can
- Compare alpha, beta and gamma by charge, range and what stops them
- Write nuclear equations for alpha and beta decay
What they copy into their notebook
Alpha: 2 protons, 2 neutrons, stopped by paper, most ionising. Beta: fast electron, stopped by aluminium. Gamma: wave, only reduced by thick lead. Alpha: mass −4, atomic −2. Beta: mass same, atomic +1. Gamma: no change.