Radioactive Emissions (WJEC GCSE Science (Double Award)): Revision Note

Radioactive Emissions

• Some atomic nuclei are unstable and radioactive

• This is because of an imbalance of protons or neutrons in the nucleus

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

• This is because it has two extra neutrons compared to a stable nucleus of carbon-12

Stable and Unstable Isotopes of Carbon

Carbon-12 is stable, whereas carbon-14 is unstable because it has two extra neutrons

• Unstable nuclei can emit radiation to become more stable

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

• This process is known as radioactive decay

• As the radiation moves away from the nucleus, it takes some energy with it

• This makes the nucleus more stable

Radioactive Decay of a Nucleus

Unstable nuclei decay by emitting high energy particles or waves

Detecting Radiation

• Radioactive decay is a random and spontaneous process

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

• This is important to understand when undertaking experimental work involving radioactive decay

• A common device used to measure and detect radiation is called a Geiger-Müller tube

• Each time it absorbs radiation, it transmits an electrical pulse to a counting machine

• This makes a clicking sound or displays the count rate

• The greater the frequency of clicks, or the higher the count rate, the more radiation the Geiger-Müller tube is absorbing

  • Therefore, it matters how close the tube is to the radiation source

  • The further away from the source, the lower the count rate detected

A Geiger-Müller Tube

A Geiger-Müller tube (or Geiger counter) is a common type of radiation detector

• To reduce the effect of random fluctuations in the measurements:

  • Readings should be repeated and averages taken

  • Background radiation must be subtracted from the readings

  • The readings should be taken over a long period of time