The time that it takes for half of a sample to decay is known as the half life of the isotope.
Some isotopes have half lives longer than the present age of the universe, but they are still subject to the same laws of quantum physics and will eventually decay, even if doing so at a time when all remaining atoms in the universe are separated by astronomical distances.
Carbon 14 has a half-life of 5,780 years, and is continuously created in Earth's atmosphere through the interaction of nitrogen and gamma rays from outer space.
Because atmospheric carbon 14 arises at about the same rate that the atom decays, Earth's levels of carbon 14 have remained fairly constant.
This decay is an example of an exponential decay, shown in the figure below.Knowing about half-lives is important because it enables you to determine when a sample of radioactive material is safe to handle.As mentioned previously, radioactive decay is the disintegration of an unstable atom with an accompanying emission of radiation.A useful application of half-lives is radioactive dating.This has to do with figuring out the age of ancient things.Here you can discover the power of geological processes.