# Half life and radioactive dating mastering physics

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.

The isotopic distribution of carbon on the Earth is roughly 99% carbon 12 (with 6 protons and 6 neutrons) and 1% carbon 13 (with 6 protons and 7 neutrons).Radiometric dating is a means of determining the "age" of a mineral specimen by determining the relative amounts present of certain radioactive elements.By "age" we mean the elapsed time from when the mineral specimen was formed.Radioactive elements "decay" (that is, change into other elements) by "half lives." If a half life is equal to one year, then one half of the radioactive element will have decayed in the first year after the mineral was formed; one half of the remainder will decay in the next year (leaving one-fourth remaining), and so forth.The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life (in other words raised to a power equal to the number of half-lives).