The half-life of a radioactive element is the time that it takes for one half of the atoms of that substance to disintegrate into another nuclear form. These can range from mere fractions of a second, to many billions of years. In addition, the half-life of a particular radionuclide is unique to that radionuclide, meaning that knowledge of the half-life leads to the identity of the radionuclide. The following is a listing of the half-lives of commonly-encountered radionuclides, with the units of each as shown.
Please note that some of the longer half-lives are written in scientific notation (i.e., 7.2E1 is equal to 7.2 x 10, or 72.)
Actinium
Americium
Antimony
Argon
Astatine
Barium
Beryllium
Bismuth
Bromine
Cadmium
Calcium
Californium
Carbon
Cerium
Cesium
Chromium
Cobalt
Copper
Curium
Europium
Fluorine
Francium
Gadolinium
Gallium
Gold
Holmium
Hydrogen
Indium
Iodine
Iridium
Iron
Krypton
Lanthanum
Lead
Manganese
Mercury
Molybdenum
Neodymium
Neptunium
Nickel
Niobium
Nitrogen
Oxygen
Palladium
Phosphorus
Plutonium
Polonium
Potassium
Praseodymium
Promethium
Protactinium
Radium
Radon
Rhenium
Rhodium
Rubidium
Ruthenium
Samarium
Scandium
Selenium
Silver
Sodium
Strontium
Sulfur
Technetium
Tellurium
Terbium
Thallium
Thorium
Tin
Tungsten
Uranium
Vanadium
Xenon
Ytterbium
Yttrium
Zinc
Zirconium