What does Edexcel Combined Science CP6 cover?

CP6 covers the structure of the atom and isotopes, the three types of nuclear radiation (alpha, beta and gamma) and their ionising and penetrating powers, nuclear decay, the meaning of half-life and activity, and the dangers and uses of radioactivity such as medical tracers and sterilisation.

What are alpha, beta and gamma radiation?

Alpha is a helium nucleus (two protons and two neutrons): most ionising, least penetrating, stopped by paper. Beta is a fast-moving electron from the nucleus: moderately ionising and penetrating, stopped by aluminium. Gamma is a high-energy electromagnetic wave: least ionising, most penetrating, reduced by thick lead or concrete.

The half-life of a radioactive isotope is the time taken for half the radioactive nuclei in a sample to decay, or equivalently for the activity to halve. Activity is measured in becquerels (decays per second). After each half-life the activity halves, so after three half-lives it is one eighth of the start.

Why is radioactivity dangerous?

Radiation is dangerous because it ionises atoms and can damage or kill living cells, and high doses can cause cancer or radiation sickness. Exposure is reduced by using shielding, keeping a distance from the source, and limiting the time of exposure.

What are the uses of radioactivity?

Gamma rays are used to sterilise medical equipment and to treat cancer, beta sources are used in thickness gauges, alpha sources are used in some smoke detectors, and radioactive isotopes are used as medical tracers and to date rocks and ancient remains by their known half-lives.

EnglandCombined Science

Edexcel GCSE Combined Science CP6 Radioactivity: a complete overview of nuclear radiation, decay and half-life

A deep-dive Edexcel GCSE Combined Science guide to Topic 6 (CP6) Radioactivity. Covers atomic structure and isotopes, alpha, beta and gamma radiation and their properties, nuclear decay, half-life and activity, and the dangers and uses of radioactivity, with the exam patterns Edexcel repeats.

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Jump to a section

What CP6 actually demands
Atomic structure and radiation
Half-life
Dangers and uses
How CP6 is examined
Check your knowledge

What CP6 actually demands

Radioactivity, on Physics Paper 1, rewards a clear understanding of the three radiations and their properties, confident half-life calculations, and a balanced view of the dangers and uses of radiation.

This guide walks through the topic and ties together the matching dot-point page, which has its own practice questions.

Atomic structure and radiation

An atom has a nucleus of protons and neutrons with electrons around it. Isotopes have the same protons but different neutrons; unstable ones are radioactive and decay randomly, emitting radiation:

Alpha - a helium nucleus; most ionising, least penetrating (paper).
Beta - a fast electron; moderate (aluminium).
Gamma - a high-energy EM wave; least ionising, most penetrating (lead/concrete).

Half-life

The half-life is the time for half the radioactive nuclei (or the activity, in becquerels) to decay. After each half-life the activity halves, so it falls quickly over several half-lives.

Dangers and uses

Radiation ionises and can damage cells, so it is dangerous, and exposure is reduced by shielding, distance and time. It is also useful: sterilising equipment, treating cancer, thickness gauges, smoke detectors, medical tracers and dating.

How CP6 is examined

Comparison. Comparing alpha, beta and gamma by composition and penetrating power.
Half-life. Calculating the activity or fraction remaining after a number of half-lives.
Properties. Matching a radiation to a use or to the right absorber.
Safety. Explaining the dangers and how to reduce exposure.

Check your knowledge

A mix of recall and calculation questions covering CP6. Attempt them under timed conditions, then check against the solutions.

What is an alpha particle made of? (1 mark)
Which radiation is the most penetrating? (1 mark)
What stops beta radiation? (1 mark)
Define half-life. (1 mark)
A source has an activity of 400 Bq and a half-life of 3 hours. What is the activity after 9 hours? (2 marks)
State one danger of radiation. (1 mark)
State one way to reduce exposure to radiation. (1 mark)
Give one use of gamma radiation. (1 mark)

Sources & how we know this

Edexcel GCSE (9-1) Combined Science (1SC0) specification — Pearson (2016)