Radioactive decay

Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable <a href="/facts/Atomic_nucleus/orpIm5Xl">atomic nucleus</a> loses energy by <a href="/facts/Radiation/RwMocyeq">radiation</a>. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are <a href="/facts/Alpha_decay/rCsHNIUE">alpha</a>, <a href="/facts/Beta_decay/vxTBlckp">beta</a>, and <a href="/facts/Gamma_ray/5Drf913J">gamma decay</a>. The <a href="/facts/Weak_force/f6upmKMs">weak force</a> is the <a href="/facts/Fundamental_interactions/WrFEJaFl">mechanism</a> that is responsible for beta decay, while the other two are governed by the <a href="/facts/Electromagnetic_force/oAkmALHT">electromagnetic</a> and <a href="/facts/Nuclear_force/A2MyJoWE">nuclear forces</a>.
Radioactive decay is a <a href="/facts/Randomness/QJQBoEX5">random</a> process at the level of single atoms. According to <a href="/facts/Quantum_mechanics/BRc3Mzgr">quantum theory</a>, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as a <a href="/facts/Decay_constant/wLB1zYDP">decay constant</a> or as a <a href="/facts/Half-life/kGVH8BAB">half-life</a>. The half-lives of radioactive atoms have a huge range: from nearly instantaneous to far longer than the <a href="/facts/Age_of_the_universe/BaByputq">age of the universe</a>.
The decaying nucleus is called the parent <a href="/facts/Radionuclide/5WpCfbdq">radionuclide</a> (or parent <a href="/facts/Isotope/KD9B1y6o">radioisotope</a>), and the process produces at least one <a href="/facts/Decay_product/hT0obfLv">daughter nuclide</a>. Except for gamma decay or <a href="/facts/Internal_conversion/mVkoudEe">internal conversion</a> from a nuclear <a href="/facts/Excited_state/czcLYNnr">excited state</a>, the decay is a <a href="/facts/Nuclear_transmutation/MjlvjsV6">nuclear transmutation</a> resulting in a daughter containing a different number of <a href="/facts/Proton/clCjepXP">protons</a> or <a href="/facts/Neutron/oRCM1geb">neutrons</a> (or both). When the number of protons changes, an atom of a different <a href="/facts/Chemical_element/0jducgWD">chemical element</a> is created.
There are 28 naturally occurring chemical elements on Earth that are radioactive, consisting of 35 <a href="/facts/Radionuclide/5WpCfbdq">radionuclides</a> (seven elements have two different radionuclides each) that date before the time of formation of the <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>. These 35 are known as <a href="/facts/Primordial_radionuclide/lFAUqHDv">primordial radionuclides</a>. Well-known examples are <a href="/facts/Uranium/n2sGWBzU">uranium</a> and <a href="/facts/Thorium/ysdWH470">thorium</a>, but also included are naturally occurring long-lived radioisotopes, such as <a href="/facts/Potassium-40/RMnkrhvc">potassium-40</a>. Each of the heavy <a href="/facts/Primordial_nuclide/lFAUqHDv">primordial radionuclides</a> participates in one of the four <a href="/facts/Decay_chain/JvTwPNBn">decay chains</a>.

Radioactive decay open-in-new

Radioactive decay