Beta Decay (Edexcel GCSE Physics: Combined Science)

• 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 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

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

• 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 (β⁺) 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 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