Decay & Transformations (Edexcel GCSE Physics)

Nuclear Transformations

• During radioactive decay, the atomic (proton) number and mass (nucleon) number of the nuclei will change

Alpha Emission

• An alpha particle consists of 2 protons and 2 neutrons (same as a helium nucleus)

• It is emitted from large unstable nuclei

Nuclear notation for an alpha particle

• When an alpha particle is emitted from a nucleus:

  • The nucleus loses 2 protons

    • The atomic (proton) number decreases by 2

  • The nucleus loses 4 particles (nucleons) in total

    • The mass (nucleon) number decreases by 4

Beta emission

Nuclear notation for beta minus and beta plus particle

• Beta minus decay is when a neutron turns into a proton emitting an electron

• When a beta minus particle is emitted from a nucleus:

  • The number of protons in the nucleus increases by 1

    • The atomic (proton) number increases by 1

  • The total number of particles in the nucleus remains the same

    • The mass (nucleon) number does not change

• Beta plus decay is when a proton turns into a neutron emitting a positron

• When a beta plus particle is emitted from a nucleus:

  • The number of protons in the nucleus decreases by 1

    • The atomic (proton) number decreases by 1

  • The total number of particles in the nucleus remains the same

    • The mass (nucleon) number does not change

Gamma Emission

Nuclear notation for a gamma particle

• Gamma waves are emitted from a nucleus when the nucleus needs to lose some energy

• This usually occurs because the nucleus has excess energy following a previous decay

• Therefore, no protons or neutrons are lost from the nucleus in this process

  • The atomic (proton) and mass (nucleon) numbers do not change

 Neutron Emission

• A small number of isotopes can decay by emitting neutrons

• When a nucleus emits a neutron:

  • The number of protons does not change

    • The atomic (proton) number does not change

  • The total number of particles (nucleons) in the nucleus decreases by 1

    • The mass (nucleon) number decreases by 1

Gamma Emission

• Nuclei that have undergone radioactive decay often undergo nuclear rearrangement with a loss of energy as gamma radiation rather than a change in the atomic structure

• A gamma ray emitted has high energy but there is no change to the mass or charge of the initial atom

  • This is because gamma rays are electromagnetic radiation that have 0 atomic and mass number

Atom emitting high energy gamma radiation