So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value.So, you might say that the 'full-life' of a radioactive isotope ends when it has given off all of its radiation and reaches a point of being non-radioactive.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.Many isotopes have been studied, probing a wide range of time scales.
Isotopes decay at an exponential rate that that can be described in terms of half-life.
One half-life is the time it takes for ½ of the parent isotopes present in a rock or bone or shell to decay to daughter isotopes.
Parent isotopes decay to daughter isotopes at a steady, exponential rate that is constant for each pair.
Some of these atomic arrangements are stable, and some are not.
The unstable isotopes change over time into more stable isotopes, in a process called radioactive decay.