It then takes the same amount of time for half the remaining radioactive atoms to decay, and the same amount of time for half of those remaining radioactive atoms to decay, and so on. The amount of time it takes for one-half of a sample to decay is called the half-life of the isotope, and it’s given the symbol: It’s important to realize that the half-life decay of radioactive isotopes is not linear.

For example, you can’t find the remaining amount of an isotope as 7.5 half-lives by finding the midpoint between 7 and 8 half-lives.

The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out.

The technique of comparing the abundance ratio of a radioactive isotope to a reference isotope to determine the age of a material is called radioactive dating.

those that form during chemical reactions without breaking down).

The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.

The nucleus contains protons (tiny particles each with a single positive electric charge) and neutrons (particles without any electric charge).

Scientists look at half-life decay rates of radioactive isotopes to estimate when a particular atom might decay.

A useful application of half-lives is radioactive dating.

This decay process leads to a more balanced nucleus and when the number of protons and neutrons balance, the atom becomes stable.

This radioactivity can be used for dating, since a radioactive 'parent' element decays into a stable 'daughter' element at a constant rate.