Radioactive half-life
When an unstable nucleus gives out an alpha or beta particle, the nucleus turns into the nucleus of a new element. This process is called
Working out the half-life allows us to calculate when a A chemical element whose atoms have unstable nuclei that can break apart or change, releasing radiation. will become stable.
Look at the diagram.
In this decay model, the green squares represent the parent unstable nuclei. They decay into the red squares – the The nucleus of a new element formed from the decay of the starting parent nucleus..
The process is random. You can’t tell when a green will turn into a red, or which green will decay, but after every half-life, half of the green parents will have decayed into red daughters.
This diagram shows the parent atoms only. Notice that they halve after every half-life.
This graph shows the pattern of the decay.
The graph starts at 16 atoms and shows the number of The initial unstable nucleus. halving every half-life.
All radioactive isotopes have a decay curve that looks like the one in the graph, however the half-life times can vary from seconds to millions of years.
The half-life of a radioactive element is the time taken for:
- the The number of decays of a radioactive element per second. Measured in Becquerels (Bq). to halve
- the number of parent nuclei to halve
- the mass of the parent nuclei to halve