The radioactivity or radioactivity is a natural or artificial, by which some substances orradioactive chemical element, are able to emit radiation, which have the property toimpress photographic plates, ionized gases, to produce fluorescence, through opaqueto light ordinary, etc. The radiation emitted by radioactive substances are mainly alphaparticles, beta particles and gamma rays. Radioactivity is a nuclear power, used in medicine (radiotherapy) and consists of some atoms like uranium, radium and thoriumare "unstable", and constantly lost alpha, beta and gamma ray (X).
