Atomic structure: GCSE Physics
Atoms and isotopes, radioactive decay, nuclear equations, half-life, irradiation versus contamination, and background radiation
The short version
Describe isotopes, compare alpha, beta and gamma, complete nuclear equations, read half-life from graphs, and contrast irradiation with contamination.
Key idea
Atomic number Z = protons; mass number A = protons + neutrons
Grade 2–3: The nucleus is tiny and heavy. Isotopes are the same element with a different mass.
Grade 5–6: I can use A and Z and I know isotopes have different numbers of neutrons.
Grade 9: Plum pudding was rejected because it could not explain large-angle deflections of alpha particles. Rutherford: tiny positive nucleus, mostly empty space. Bohr: electrons in shells. Chadwick: neutron. I never say isotopes are different elements.
Go a bit deeper
Beta comes from a neutron changing into a proton + electron
Grade 2–3: Alpha is stopped easily. Gamma goes through a lot. You cannot say which atom will decay next.
Grade 5–6: I can name what each radiation is and what thickness stops it.
Grade 9: Short range highly ionising (alpha). Long range weakly ionising (gamma). Beta is not an electron from a shell. Alpha is not a helium atom (no electrons).
Worked example
Worked example
Grade 2–3: The nucleus is tiny and heavy. Isotopes are the same element with a different mass. Grade 5–6: I can use A and Z and I know isotopes have different numbers of neutrons. Grade 9: Plum pudding was rejected because it could not explain large-angle deflections of alpha particles. Rutherford: tiny positive nucleus, mostly empty space. Bohr: electrons in shells. Chadwick: neutron. I never say isotopes are different elements.
Lessons in this topic
- Atoms isotopes
- Radioactive decay
- Nuclear equations
- Half-life
- Irradiation vs contamination
- Background radiation
In the app each lesson is video (when we have a real YouTube id) then intro, learn and summary steps.
What the examiner wants
Alpha is He nucleus (stopped by paper); beta is a high-speed electron from the nucleus; gamma is a wave. Half-life is time for activity or undecayed nuclei to halve. Combined does not examine fission and fusion.
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
The atomic number of an atom is the number of
Isotopes of an element have
Rutherford’s alpha scattering showed that
Alpha radiation is
Common mistakes
- Isotopes are not "different elements". Same proton number means same element.
- Beta is not an electron from a shell. It is produced in the nucleus. Alpha is not a helium atom (no electrons).
- Do not decrease Z for beta-minus. Students mix it up with alpha. Gamma does not change the isotope numbers.
- Do not divide the activity by 2 and call that the half-life. Half-life is a time.
Answers and working
Frequently asked questions
Is GCSE Atomic structure on Combined Science and Triple?
Atomic structure is on Combined Science and on Triple Physics. Progress is shared in the ReviseEasy app.
Which exam board is this Atomic structure page for?
The ideas are board-agnostic for AQA, Edexcel, OCR, WJEC and CCEA. Paper lengths and question numbers differ — check your specification.
Is Atomic structure Foundation or Higher?
The core ideas appear on both tiers. Higher papers add extra application and some HT-only detail, marked in lessons with a Higher badge.
Learn, try, get feedback, fix the mistake
Open the stepped lesson, then the quiz with hints. Required-practical and calculation questions use the same method you will need in the paper.
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