radioaktivita
Radioaktivita, or radioactivity, is the spontaneous decay of unstable atomic nuclei, accompanied by emission of ionizing radiation in the form of alpha particles (helium nuclei), beta particles (electrons or positrons), and gamma rays. Some decays also emit neutrons or produce X-rays. The process is random at the level of individual nuclei but predictable on average via statistics.
Each radioactive isotope has a characteristic half-life, the time required for half of a sample to decay.
Natural sources include primordial radionuclides such as uranium and thorium in rocks, and radon gas from soil.
Radioactivity is quantified by activity in becquerels, representing decays per second. Doses are expressed in gray
Radioactivity has wide uses: in medicine for diagnosis and treatment (radiopharmaceuticals, radiotherapy), in industry for imaging
The discovery of radioactivity in 1896 by Henri Becquerel, followed by work of Marie and Pierre Curie,