Radioactivity | Edexcel GCSE Combined Science Physics, Higher tier (1SC0)

Radioactivity

201 questions
16 subtopics
Paper 5
Paper 5

Radioactivity is examined in Paper 5, Physics 1.

It covers the atom and the size of atoms, isotopes, atomic number and mass number, relative masses and charges of subatomic particles, electron orbits and energy levels, forming ions, and how the atomic model changed, types of ionising radiation, background radiation and detecting radioactivity, alpha, beta and gamma, and their penetrating power, beta-minus and beta-plus decay, effects of decay on atomic number and mass number, balancing nuclear equations, activity and the becquerel, half-life and the randomness of decay, half-life calculations, the dangers of ionising radiation and safety precautions, contamination and irradiation.

Sample questions from Radioactivity

Answer each one closed book first, then open the answer.

The atom and the size of atoms

Why is almost all the mass of an atom concentrated in its nucleus?

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Protons and neutrons are nearly two thousand times more massive than electrons, and both sit in the nucleus.
Relative masses and charges of subatomic particles

How does a positron compare with an electron?

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A positron has the same tiny mass as an electron but the opposite, positive charge.
Forming ions, and how the atomic model changed

Describe the plum pudding model of the atom.

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It pictured an atom as a ball of positive charge with negative electrons dotted through it.
Background radiation and detecting radioactivity

Name three natural sources of background radiation that originate on Earth.

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Rocks and soil, building materials such as granite, and food and drink.
Beta-minus and beta-plus decay

Which nuclei are likely to decay by β⁻ emission?

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Nuclei that have too many neutrons compared with their number of protons.
Balancing nuclear equations

How is a β⁻ particle written in a nuclear equation?

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It is written as ⁰₋₁e, with a mass number of 0 and a charge of −1.
Half-life and the randomness of decay

Does the half-life of an isotope depend on how large a sample you start with?

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No, the half-life is the same whatever the size of the sample.
The dangers of ionising radiation

Why is even a low dose of ionising radiation still a risk?

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It can cause a mutation in a single cell that later develops into a cancer.

The 16 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
The atom and the size of atoms	Protons, neutrons and electrons and where they sit, the tiny dense positive nucleus, atoms as mostly empty space, the sizes of atoms, molecules and nuclei in standard form, and the symbols <<, >> and ~.	14
Isotopes, atomic number and mass number	What atomic number and mass number count, finding neutrons by subtraction, reading nuclear symbols, what isotopes are, and why carbon-12 and carbon-14 react identically.	13
Relative masses and charges of subatomic particles	Relative masses and charges of the proton, neutron, electron and positron, why electrons add almost no mass, why a complete atom is neutral, matching numbers of protons and electrons, and how an extra electron makes a negative ion.	12
Electron orbits and energy levels	Electrons orbiting at fixed distances called energy levels, why outer electrons are held least tightly, moving between levels by absorbing or emitting electromagnetic radiation, why only certain energies are absorbed, and how atoms give out light or ionise.	11
Forming ions, and how the atomic model changed	Ions and ionisation, how atoms become positive ions, the plum pudding model, alpha particle scattering in Rutherford's laboratory, the nuclear and Bohr models, why models of the atom changed, and peer review and communicating scientific results.	20
Types of ionising radiation	The five types of radiation emitted by unstable nuclei, why radioactive decay is random and unaffected by conditions, what ionising radiation does to atoms, and why strongly ionising radiation loses energy and cannot travel far.	11
Background radiation and detecting radioactivity	Background radiation and correcting count rates for it, natural sources such as radon, rocks, food and cosmic rays, sources from human activity, doses for aircraft crew, and detecting radiation with photographic film, film badges and Geiger–Müller tubes.	18
Alpha, beta and gamma, and their penetrating power	What alpha particles, beta minus particles and gamma rays are, their mass numbers, atomic numbers and charges, their ionising and penetrating power, what stops each one, and identifying a source from what absorbs its radiation.	15
Beta-minus and beta-plus decay	What happens inside a nucleus during β⁻ and β⁺ decay, how the numbers of protons and neutrons, the charge and the mass number change, which nuclei decay each way, and the differences between the two decays.	12
Effects of decay on atomic number and mass number	How alpha, beta-minus, beta-plus, gamma and neutron emission each change mass number and atomic number, worked examples, and why a gamma ray often follows another decay.	14
Balancing nuclear equations	Balancing mass number and charge in a nuclear equation, finding an unknown nucleus or particle, and how β⁻ particles and positrons are written.	9
Activity and the becquerel	Activity as the number of nuclei decaying each second, why it falls over time and the shape of its graph, the becquerel and what 1 Bq means, and calculating decays or activity from counts over a time.	9
Half-life and the randomness of decay	Half-life defined by undecayed nuclei and by activity, the fraction left after one or two half-lives, and why random decay still gives reliable predictions for a large sample.	11
Half-life calculations	Activity or nuclei remaining after a number of half-lives, finding a half-life from a fall in activity or from a graph, and the percentage left after three half-lives.	9
The dangers of ionising radiation	How ionising radiation damages cells and DNA, high and low doses, keeping dose, time and closeness to a source low, and school laboratory precautions.	9
Safety precautions, contamination and irradiation	Protective clothing, screens, lead aprons, low medical doses and film badges, shielding gamma radiation with lead or concrete, irradiation versus contamination, why alpha sources are most dangerous inside the body, and precautions against contamination.	14

Radioactivity is 201 of the 1,449 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.