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Radioactive Decay

Physics: AQA GCSE Higher, topic 4.2.14

Radioactive Decay

During alpha, beta, and gamma radioactive decay, an unstable nucleus becomes more stable.

Alpha decay

Alpha decay

  • In alpha decay, a nucleus loses an alpha particle.
  • An alpha particle is made from 2 protons and 2 neutrons.
  • Because 2 protons have been lost, we now have a new element.
Alpha decay equation

Alpha decay equation

  • Polonium undergoes alpha decay in the equation:
  • 21884Po→21482Pb+42α{{{218}\atop{84} }\text{Po}} \rightarrow {{{214}\atop{82} }\text{Pb}} + {{{4}\atop{2} }{\alpha}}
Beta decay

Beta decay

  • In beta decay, a neutron in the nucleus decays to form a proton and electron.
  • This electron is then ejected out of the nucleus.
Beta decay equations

Beta decay equations

  • Carbon undergoes beta decay in the equation:
  • 146C→147N+0−1β{{{14}\atop{6} }\text{C}} \rightarrow {{{14}\atop{7} }\text{N}} + {{{0}\atop{-1} }{\beta}}
Gamma decay

Gamma decay

  • In gamma decay, the composition of the nucleus is unchanged.
  • The nucleus is said to be “relaxing” from one state into another state with lower energy.
Gamma decay equations

Gamma decay equations

  • Iodine undergoes gamma radiation in the equation:
  • 12553I→12553I+00γ{{{125}\atop{53} }\text{I}} \rightarrow {{{125}\atop{53} }\text{I}} + {{{0}\atop{0} }{\gamma}}

Test yourself on Radioactive Decay

  • Which of these equations shows alpha decay?

  • Which of these equations shows beta decay?

  • Which of these equations shows gamma decay?

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