Radioactive Decay (Oxford AQA IGCSE Physics)

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

• 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

• 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

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

• 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