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. Decay produces daughter nuclides and may proceed through decay chains with successive steps until a stable nucleus is reached. Ionizing radiation can ionize atoms in matter, causing damage.

Natural sources include primordial radionuclides such as uranium and thorium in rocks, and radon gas from soil. Cosmic radiation from space also contributes. Artificial sources arise from nuclear reactors, medical isotopes, industrial radiography, research activities, and past atmospheric nuclear testing.

Radioactivity is quantified by activity in becquerels, representing decays per second. Doses are expressed in gray (absorbed dose) and sievert (equivalent dose), accounting for biological effect. Protection relies on limiting exposure time, increasing distance, and using shielding and containment to reduce dose.

Radioactivity has wide uses: in medicine for diagnosis and treatment (radiopharmaceuticals, radiotherapy), in industry for imaging and material testing, in science for dating and tracing processes, and in power generation through controlled nuclear fission. All uses require regulatory controls and safety practices to minimize risks to people and the environment.

The discovery of radioactivity in 1896 by Henri Becquerel, followed by work of Marie and Pierre Curie, marked a turning point in physics and medicine. The field continues to be regulated to manage health and environmental risks.