Year 9 Science Exam Prep — Episode 9: Atomic Structure and Radioactivity (2026)

Episode Overview

In this lecture-style revision episode, your science teacher walks you through everything you need to know about Atomic Structure and Radioactivity for your Year 9 science exam — from scratch, step by step.

Topics covered in this episode:

Subatomic particles: protons, neutrons, and electrons (charges, masses, locations)
Atomic number and mass number — how to calculate the number of neutrons
Isotopes — what they are, why they have the same chemical properties, and the carbon-14 dating example
The development of the nuclear model: Dalton → Thomson's plum pudding model → Rutherford's gold foil experiment → Bohr's electron shells → Chadwick's neutron
The gold foil experiment: what was expected, what was observed, and what it proved
The three types of radioactive decay: alpha, beta, and gamma — properties, penetration, ionising power, and dangers
Writing and balancing nuclear equations for alpha and beta decay
Half-life: what it means, worked calculation examples, and how to work backwards
Uses of radioactivity: medical tracers, radiotherapy, carbon dating, smoke detectors, nuclear power
Dangers of radiation and safety measures

Exam Tips Covered

Always check mass numbers and atomic numbers balance on both sides of a nuclear equation.
For half-life calculations, count half-lives first — never divide the amount directly by time.
For the gold foil experiment, describe what was observed and then explain what it tells us.
Always state whether a radiation hazard question is about internal or external exposure.
Learn key half-lives: Carbon-14 (~5,730 years), Americium-241 (~432 years), Iodine-131 (~8 days).

Revision Suggestion

After listening, close your eyes and write down from memory:

The subatomic particles table (particle, location, charge, mass)
The alpha / beta / gamma comparison table
One worked half-life calculation

Active recall is the most effective revision technique. Keep going — you're doing brilliantly.

Episode Overview

Topics covered in this episode:

Subatomic particles: protons, neutrons, and electrons (charges, masses, locations)

Atomic number and mass number — how to calculate the number of neutrons

Isotopes — what they are, why they have the same chemical properties, and the carbon-14 dating example

The development of the nuclear model: Dalton → Thomson's plum pudding model → Rutherford's gold foil experiment → Bohr's electron shells → Chadwick's neutron

The gold foil experiment: what was expected, what was observed, and what it proved

The three types of radioactive decay: alpha, beta, and gamma — properties, penetration, ionising power, and dangers

Writing and balancing nuclear equations for alpha and beta decay

Half-life: what it means, worked calculation examples, and how to work backwards

Uses of radioactivity: medical tracers, radiotherapy, carbon dating, smoke detectors, nuclear power

Dangers of radiation and safety measures

Exam Tips Covered

Always check mass numbers and atomic numbers balance on both sides of a nuclear equation.

For half-life calculations, count half-lives first — never divide the amount directly by time.

For the gold foil experiment, describe what was observed and then explain what it tells us.

Always state whether a radiation hazard question is about internal or external exposure.

Learn key half-lives: Carbon-14 (~5,730 years), Americium-241 (~432 years), Iodine-131 (~8 days).

Year 9 Science Exam Prep — Episode 9: Atomic Structure and Radioactivity

Episode Overview

Exam Tips Covered

Revision Suggestion

Related content

Year 9 Science Exam Prep — Episode 9: Atomic Structure and Radioactivity

Episode Overview

Exam Tips Covered

Revision Suggestion

Related content