Radioactive Decay

Key Stage 4

Radioactive decay is when an unstable isotope emits a particle or electromagnetic wave to become more stable.

During a radioactive decay an unstable isotope may emit:

The rate of radioactive decay is known as the 'Half Life' which is how long it takes for half of the unstable isotopes in a sample of radioactive material to decay. This time is a constant for each type of radioactive material regardless of the quantity of unstable isotopes.

	This is a key to show the types of particles in the following decays of unstable nuclei.


This nucleus is unstable because it is too massive and has too few neutrons relative to protons so it decays via alpha emission reducing the atomic mass by 4 and the atomic number by 2. \({}_Z^AX \rightarrow {}_{Z-2}^{A-4}Y + {}_2^4\alpha\)	This nucleus is unstable because it is too many neutrons so it decays via beta emission in which a neutron turns into a proton increasing the atomic number by 1. \({}_Z^AX \rightarrow {}_{Z+1}^{A}Y + {}_{-1}^0\beta\)


This nucleus is unstable because it is has excess vibrational energy so it decays by emitting a gamma ray. After the decay it still has the same atomic mass and atomic number but is no longer vibrating. \({}_Z^AX \rightarrow {}_Z^AX + {}_0^0\gamma\)	This nucleus is unstable because it has too many neutrons relative to protons so it decays via neutron radiation reducing the atomic mass by 1. \({}_Z^AX \rightarrow {}_{Z}^{A-1}Y + {}_0^1n\)