Radioactivity

Property of certain substances to convert without external effect, emitting a characteristic radiationEnergy dispersion through matter or space. In atomic physics.... Radioactivity was discovered for uraniumNatural radioactive element with the atomic number 92. The n... by BecquerelUnit of activity of a radionuclide named after Henri Becquer... in 1896. If the substances, or to be more precise, the radionuclides occur in nature, one refers to natural radioactivity; if they are a product of nuclear conversions in nuclear reactors or accelerators, one refers to artificial radioactivity. More than 2,750 radionuclides are known today. Each radionuclideUnstable nuclide spontaneously decaying without external eff... is characterized by its half-lifeThe period during which half of the nuclei decay in a quanti..., the time during which half the atomic nuclei convert in a given quantity. Half-lives of several billion years (uranium-238; even still longer-lived is tellurium-128 with a half-lifeThe period during which half of the nuclei decay in a quanti... of 7.2·1024 years) to the millionth of a second (Po-212) are known. The radiationEnergy dispersion through matter or space. In atomic physics... emitted during decayThe spontaneous conversion of a nuclide into another nuclide... and its energyAbility to do work or diffuse heat. The unit of energy is th... is also characteristic. For example, radium-226 decays emitting alpha radiationEnergy dispersion through matter or space. In atomic physics..., while iodine-131 emits beta rays.