How to Calculate the Percent Abundance of an Isotope.
These radioactive isotopes are unstable, decaying over time at a predictable rate. All ordinary matter is made up of combinations of chemical elements , each with its own atomic number , indicating the number of protons in the atomic nucleus. The most common is U There are several common radioactive isotopes that are used for dating rocks, artifacts and fossils. Dating methods based on extinct radionuclides can also be calibrated with the U-Pb method to give absolute ages. The half-life of C, however, is only 5, years. Another example of short-lived extinct radionuclide dating is the 26 Al — 26 Mg chronometer, which can be used to estimate the relative ages of chondrules.