Radioisotopes in radioactive dating
Radionuclides that find their way into the environment may cause harmful effects as radioactive contamination.
They can also cause damage if they are excessively used during treatment or in other ways exposed to living beings, by radiation poisoning.
For example, polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10 Further radionunclides may occur in nature in virtually undetectable amounts as a result of rare events such as spontaneous fission or uncommon cosmic ray interactions.
A pharmaceutical drug made with radionuclides is called a radiopharmaceutical.A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess nuclear energy, making it unstable.This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferred to one of its electrons to release it as a conversion electron; or used to create and emit a new particle (alpha particle or beta particle) from the nucleus.Elements heavier than lead, and the elements technetium and promethium, exist only as radionuclides.(In theory, elements heavier than dysprosium exist only as radionuclides, but the half-life for some such elements, e.g. Unplanned exposure to radionuclides generally has a harmful effect on living organisms including humans, although low levels of exposure occur naturally without harm.