Radioactive forms of elements are called radionuclideRadioactive forms of elements are called radionuclides. Radium-226, Cesium-137, and Strontium-90 are examples of radionuclides.. Some occur naturally in the environment, while others are man-made, either deliberately or as byproducts of nuclear reactions. Learn the Radiation Basics.
Every radionuclide emits radiation at its own specific rate, which is measured in terms of half-life. Radioactive half-life is the time required for half of the radioactive atoms present to decay. Radioactive decay is when a radioisotope transforms into another radioisotope; this process emits radiation in some form. Some radionuclides have half-lives of mere seconds, but others have half-lives of millions of years. Learn more about radioactive decay.
Below you will find links to basic information about twelve radionuclides encountered in medical, commercial, and military activities. These pages contain information about the properties of the element, how it moves through the environment, where you may find it (the radiation source) and potential health effects.