Radioactive Decay (Oxford AQA IGCSE Physics)

Revision Note

Radioactive Decay

Unstable nuclei

  • Some atomic nuclei are unstable

  • Carbon-14 is an isotope of carbon which is unstable

    • It has two extra neutrons compared to stable carbon-12

Carbon-12 and Carbon-14

The nucleus of carbon-14 contains an imbalance of protons and neutrons and is unstable, IGCSE & GCSE Physics revision notes
Carbon-12 is stable, whereas carbon-14 is unstable. This is because carbon-14 has two extra neutrons
  • Some isotopes are unstable because of their large size or because they have too many or too few neutrons

Radiation

  • Unstable nuclei can emit radiation to become more stable

    • Radiation can be in the form of a high-energy particle or wave

Radiation emitted from a nucleus

Radioactive decay of a nucleus by the emission of radiation, IGCSE & GCSE Physics revision notes
Unstable nuclei decay by emitting high-energy particles or radiation
  • As the radiation moves away from the nucleus, it takes some energy with it

    • This reduces the overall energy of the nucleus

    • This makes the nucleus more stable

  • The process of emitting radiation is called radioactive decay

  • Radioactive decay is a random process

    • This means it is not possible to know exactly when a particular nucleus will decay

Worked Example

Which of the following statements is not true?

A

Isotopes can be unstable because they have too many or too few neutrons

B

The process of emitting particles or waves of energy from an unstable nucleus is called radioactive decay

C

Scientists can predict when a nucleus will decay

D

Radiation refers to the particles or waves emitted from a decaying nucleus

Answer:  C

  • Answer A is true. The number of neutrons in a nucleus determines the stability

  • Answer B is true. This is a suitable description of radioactive decay

  • Answer D is true. Radiation is about emissions. It is different to radioactive particles

  • Answer C is not true

    • Radioactive decay is a random process

    • It is not possible to predict precisely when a particular nucleus will decay

Examiner Tips and Tricks

The terms unstable, random and decay have very particular meanings in this topic. Remember to use them correctly when answering questions!

Detecting radiation

  • Radiation that is emitted from an unstable nucleus can be detected in different ways

    • For example, photographic film changes colour when exposed to radiation

  • A Geiger-Muller tube is a device used to detect radiation

A Geiger-Muller tube

Geiger-Muller tube, also called a Geiger counter, for IGCSE & GCSE Physics revision notes
This Geiger-Muller Tube is connected to a Geiger Counter. This a common way of detecting radiation and measuring a count-rate
  • Within the Geiger-Muller tube, ions are created by radiation passing through it

  • The Geiger-Muller tube can be connected to a Geiger counter

  • This counts the ions created in the Geiger-Muller tube

  • The count rate is the number of decays recorded each second by a detector

Last updated:

You've read 0 of your 10 free revision notes

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Caroline Carroll

Author: Caroline Carroll

Expertise: Physics Subject Lead

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.

Lucy Kirkham

Author: Lucy Kirkham

Expertise: Head of STEM

Lucy has been a passionate Maths teacher for over 12 years, teaching maths across the UK and abroad helping to engage, interest and develop confidence in the subject at all levels.Working as a Head of Department and then Director of Maths, Lucy has advised schools and academy trusts in both Scotland and the East Midlands, where her role was to support and coach teachers to improve Maths teaching for all.