This topic covers how a nucleus differs from the rest of the atom, what alpha, beta and gamma radiation are, how to write a balanced nuclear equation, and how to read count-rate data. It sits near the end of the IGCSE Physics learning guide and follows induction and transformers. Check the current Cambridge IGCSE Physics 0625 syllabus for the exact statements you need, because wording and scope can change between exam years.
What do you need before starting?
You should be comfortable with the idea that atoms contain protons, neutrons and electrons, and that charge and mass are properties we can compare. You also need basic ratio skills for half-life, and careful reading of tables and graphs.
If charge and fields are shaky, revisit magnetism and fields first, because alpha and beta deflection depends on it.
An orienting example
Radium-226 has 88 protons and a nucleon number of 226. It emits an alpha particle, which is a helium nucleus with 2 protons and a nucleon number of 4.
Nucleon number after decay: 226 − 4 = 222. Proton number after decay: 88 − 2 = 86. The new nucleus has 86 protons, so it is radon-222.
Notice three things. The change happened inside the nucleus, so the element changed.
The upper numbers and the lower numbers each balance on both sides. And nothing about this depended on temperature or chemical bonding.
In what order should you study the lessons?
- Distinguish atomic and nuclear changes: this fixes where each process happens, which stops the most common category error.
- Balance a simple nuclear equation: a precise, rule-based skill that is easy to practise.
- Compare radiation properties descriptively: builds the comparison table you need for short-answer questions.
- Interpret random count-rate data: connects half-life, background radiation and randomness.
- Separate ionising behaviour from penetration: ties the properties together with one cause-and-effect idea.
Then try the mixed practice set without notes.
What traps catch students in this topic?
- Treating a change of electron arrangement and a nuclear decay as the same kind of event.
- Changing the upper number but forgetting the lower number in an equation, or the reverse.
- Reading a count-rate graph without subtracting background radiation.
- Saying “alpha is the most dangerous” without saying whether the source is inside or outside the body.
- Writing that radioactive decay “can be sped up by heating”.
How should you use the practice set?
Attempt the questions on paper, with a periodic table or a list of symbols only if your exam would provide one. Mark each wrong answer by error type, not just by question number, and go back to the lesson that matches. The mistake log and retest queue is a good place to keep those error types.
Students who understand each lesson but still slip on mixed questions often benefit from a teacher watching their working. That is part of what we do in online one-to-one Physics tuition.