Radioactivity

What Radioactivity covers

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.

The 16 subtopics

Each one has its own page.

• The atom and the size of atomsProtons, 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 ~.Open →
• Isotopes, atomic number and mass numberWhat 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.Open →
• Relative masses and charges of subatomic particlesRelative 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.Open →
• Electron orbits and energy levelsElectrons 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.Open →
• Forming ions, and how the atomic model changedIons 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.Open →
• Types of ionising radiationThe 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.Open →
• Background radiation and detecting radioactivityBackground 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.Open →
• Alpha, beta and gamma, and their penetrating powerWhat 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.Open →
• Beta-minus and beta-plus decayWhat 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.Open →
• Effects of decay on atomic number and mass numberHow 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.Open →
• Balancing nuclear equationsBalancing mass number and charge in a nuclear equation, finding an unknown nucleus or particle, and how β⁻ particles and positrons are written.Open →
• Activity and the becquerelActivity 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.Open →
• Half-life and the randomness of decayHalf-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.Open →
• Half-life calculationsActivity 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.Open →
• The dangers of ionising radiationHow ionising radiation damages cells and DNA, high and low doses, keeping dose, time and closeness to a source low, and school laboratory precautions.Open →
• Safety precautions, contamination and irradiationProtective 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.Open →

What you need to know

Answer each one before you reveal it.

Take Radioactivity further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Atomic number vs Mass number

  Atomic number: the count of protons in a nucleus. Mass number: the total count of protons and neutrons in a nucleus.

• Alpha particle vs Beta minus particle

  Alpha particle: two protons and two neutrons, the same as a helium nucleus. Beta minus particle: a fast-moving electron thrown out of the nucleus.

• Irradiation vs Contamination

  Irradiation: being exposed to radiation from a source outside the body or object. Contamination: having unwanted radioactive atoms on the surface of, or inside, an object.

Questions from this topic

Each one with the model answer underneath.

1. 1

   Which two types of particle are found in the nucleus of an atom?

   Model answer

   Protons and neutrons are found in the nucleus.

2. 2

   What is the overall electric charge of the nucleus of an atom, and which particle gives it that charge?

   Model answer

   The nucleus is positively charged, because of the protons it contains.

3. 3

   Where are the electrons of an atom found, and what charge do they carry?

   Model answer

   They are found orbiting outside the nucleus and carry a negative charge.

4. 4

   How does the radius of a nucleus compare with the radius of the whole atom?

   Model answer

   The nuclear radius is far smaller, roughly ten thousand times smaller than the atomic radius.

5. 5

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

   Model answer

   Protons and neutrons are nearly two thousand times more massive than electrons, and both sit in the nucleus.

6. 6

   An atom is often described as mostly empty space. Explain why.

   Model answer

   The nucleus and the electrons take up only a tiny fraction of the atom's volume, with nothing in between.

What is inside Levo

Six ways to work the same material.

Radioactivity revision questions

What does Radioactivity cover in Edexcel GCSE Combined Science Physics?

16 subtopics: 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. Each one has its own page with questions and model answers.

How is Radioactivity organised?

By the Edexcel 1SC0 specification, subtopic by subtopic, so it matches the order you are taught it in.