GCSE Physics revision

Nuclear equations

Atoms and nuclear radiation

AQA 4.4.2.2

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AQA student objectives

Learning pathway

ALL 🎯

Use the names and symbols of common nuclei and particles to write balanced equations that show single alpha (α) and beta (β) decay.

MOST 🎯🎯

Apply nuclear equations knowledge to a relevant numerical or graphical problem and show the working.

SOME 🎯🎯🎯

Analyse an unfamiliar problem involving nuclear equations and justify the method or conclusion.

Revision summary

Read on screen, then print for Cornell-style active revision.

Elements exist as isotopes, which have the same number of protons but different numbers of neutrons.
Most isotopes are unstable and undergo radioactive decay, emitting radiation to become more stable.
A material is described as radioactive when it consists of unstable isotopes that can decay.

Alpha particles consist of two protons and two neutrons, identical to a helium nucleus, and are represented by the symbol He.
Because alpha particles have no electrons, they carry an overall charge of 2+.
Their relatively large size means they are stopped easily — travelling only a few centimetres in air and absorbed by a single sheet of paper.
Despite low penetration, their large size and strong charge make them highly ionising, readily knocking electrons off atoms they collide with.

2. Alpha ParticlesAQA

Alpha particles consist of two protons and two neutrons, identical to a helium nucleus, and are represented by the symbol He.
Because alpha particles have no electrons, they carry an overall charge of 2+.
Their relatively large size means they are stopped easily — travelling only a few centimetres in air and absorbed by a single sheet of paper.
Despite low penetration, their large size and strong charge make them highly ionising, readily knocking electrons off atoms they collide with.

Beta particles are high-speed electrons with a charge of −1 and virtually no mass.
They are produced when a neutron in the nucleus decays into a proton and an electron;
the proton remains in the nucleus while the electron is emitted.
Beta particles are moderately ionising and have moderate penetration, requiring several metres of air or approximately 5 mm of aluminium to stop them.

3. Beta ParticlesAQA

Beta particles are high-speed electrons with a charge of −1 and virtually no mass.
They are produced when a neutron in the nucleus decays into a proton and an electron;
the proton remains in the nucleus while the electron is emitted.
Beta particles are moderately ionising and have moderate penetration, requiring several metres of air or approximately 5 mm of aluminium to stop them.

Gamma rays are not particles but waves of electromagnetic radiation, similar in nature to light.
They are commonly emitted after alpha or beta decay as the nucleus releases excess energy.
Having no mass or charge, gamma rays pass straight through materials rather than colliding with atoms, making them only weakly ionising.
Gamma rays are highly penetrating, travelling long distances through air and requiring thick lead sheets or several metres of concrete to be absorbed.

4. Gamma RaysAQA

Gamma rays are not particles but waves of electromagnetic radiation, similar in nature to light.
They are commonly emitted after alpha or beta decay as the nucleus releases excess energy.
Having no mass or charge, gamma rays pass straight through materials rather than colliding with atoms, making them only weakly ionising.
Gamma rays are highly penetrating, travelling long distances through air and requiring thick lead sheets or several metres of concrete to be absorbed.

Neutron emission occurs when a nucleus contains too many neutrons, making it unstable, so it ejects a neutron to become more stable.
Neutrons have no charge and a relative mass of 1, and their emission directly reduces the neutron count in the nucleus.

Alpha particles are the least penetrating and are stopped by a single sheet of paper.
Beta particles have moderate penetration and are stopped by a thin sheet of aluminium (approximately 5 mm).
Gamma rays are the most penetrating and require thick lead or several metres of concrete to be stopped.

6. Comparing Penetration of Each Radiation TypeAQA

Alpha particles are the least penetrating and are stopped by a single sheet of paper.
Beta particles have moderate penetration and are stopped by a thin sheet of aluminium (approximately 5 mm).
Gamma rays are the most penetrating and require thick lead or several metres of concrete to be stopped.

Alpha particles are strongly ionising due to their large size and 2+ charge.
Beta particles are moderately ionising because they are smaller and carry only a −1 charge.
Gamma rays are weakly ionising as they have no mass or charge and tend to pass through matter without interacting with atoms.

7. Comparing Ionising Power of Each Radiation TypeAQA

Alpha particles are strongly ionising due to their large size and 2+ charge.
Beta particles are moderately ionising because they are smaller and carry only a −1 charge.
Gamma rays are weakly ionising as they have no mass or charge and tend to pass through matter without interacting with atoms.