The half-life of a radioactive
isotope is the amount of time it takes for half of the radioactive atoms in a
sample to decay. In other words, after one half-life, half of the original
radioactive atoms will have decayed into another element.
Half-lives of radioactive isotopes can range from
fractions of a second to billions of years, depending on the isotope. The
half-life of a particular isotope is a fixed property that does not change over
time, and it is an important factor in determining the amount of time it takes
for a sample of radioactive material to become safe.
In some cases, the half-life of a radioactive
isotope is used in radiometric dating to determine the age of rocks and other
ancient materials. The age of a sample can be estimated by measuring the amount
of the original radioactive isotope and the amount of the isotope that it has
decayed into. By knowing the half-life of the isotope and the amounts of each
isotope in the sample, the age of the sample can be calculated.