Radioactive Decay
![](../../../graphics/diagrams/radioactivity/decay.png)
Radioactive decay
is the process of the random, spontaneous transformation of a radionuclide by the emission of nuclear radiation.
It is 'spontaneous' because we cannot 'make it happen' by changing the conditions the sample is in - such as making it hotter or putting it under pressure. Similarly we cannot stop it happening - that is why nuclear waste is such a problem!
The
emission of the nuclear radiation is a purely random event. It cannot be predicted exactly when
an atom will decay, only that a certain number will decay
in a given time. The mathematics of probability is used for
this requires a large number of atoms to be considered. (See half life and radioactive
decay series).
Radioactive
nuclear decay occurs whenever a nucleus is in an energy-state
that is not the lowest possible for its nucleon
number. This state may occur naturally (which essentially
means that it was created in that state when formed within a
star) or by artificial means (neutron or photon irradiation).
![](../../../graphics/Dividers/spectbar550.gif)
The nucleus remaining is called the decay
product or daughter nucleus.
The rate of decay depends on the number of undecayed nuclei present,
so with each decay event there is a decrease in the activity of a radioactive sample.
See here for the five types of nuclear radiation.
See here for the dangers of nuclear radiation.
![](../../../graphics/Dividers/spectbar550.gif)
For a more mathematical look at this - see here