Beta Decay (Edexcel GCSE Physics)

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Beta-Minus Decay

  • Beta (β) particles are high energy electrons emitted from the nucleus
    • β particles are emitted by nuclei that have too many neutrons

  • During beta decay, a neutron changes into a proton and an electron
    • The electron is emitted and the proton remains in the nucleus

  • A completely new element is formed because the atomic number changes

Beta minus decay GCSE, downloadable IGCSE & GCSE Physics revision notes

Beta-minus decay often happens in unstable nuclei that have too many neutrons. The mass number stays the same, but the atomic number increases by one

  • An electron has a mass number of 0
    • This is because electrons have a negligible mass, compared to neutrons and protons

  • Therefore, the mass number of the decaying nuclei remains the same
  • Electrons have an atomic number of -1
    • This means that the new nuclei will increase its atomic number by 1 in order to maintain the overall atomic number before and after the decay

  • The following equation shows carbon-14 undergoing beta decay
    • It forms nitrogen-14 and a beta minus particle

  • Beta minus particles are written as an electron in this equation

Beta decay equation, downloadable IGCSE & GCSE Physics revision notes

The carbon nucleus emits a beta particle, causing its charge to increase. This means it changes into a new element

Beta-Plus Decay

  • Beta (β+) particles are high energy positrons (anti-matter of electrons) also emitted from the nucleus
    • β+ particles are emitted by nuclei that have too many protons

  • During beta plus+) decay a proton turns into a neutron emitting a positron (anti-electron)
    • The positron is emitted and the neutron remains in the nucleus

  • A completely new element is formed because the atomic number changes

Beta plus decay GCSE, downloadable IGCSE & GCSE Physics revision notes

Beta-plus decay often happens in unstable nuclei that have too many protons. The mass number stays the same, but the atomic number decreases by one

  • A positron has a mass number of 0
    • This is because the positrons have a negligible mass, just like the electron, compared to neutrons and protons

  • Therefore, the mass number of the decaying nuclei remains the same
  • Positrons have an atomic number of +1
    • This means that the new nuclei will decrease its atomic number by 1 in order to maintain the overall atomic number before and after the decay

Examiner Tip

One way to remember which particle decays into which depends on the type of beta emission, think of beta ‘plus’ as the ‘proton’ that turns into the neutron

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Ashika

Author: Ashika

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.