Radioactivity | Definition, Types, Applications, & Facts | Britannica
Sep 24, 2024 · Radioactivity, property exhibited by certain types of matter of emitting energy and subatomic particles spontaneously. It is, in essence, an attribute of individual atomic nuclei. Radioactive decay is a property of several naturally occurring elements as well as of artificially produced isotopes of the elements.
Atom - Radioactivity, Particles, Discovery | Britannica
Oct 8, 2024 · Marie coined the term radioactivity for the spontaneous emission of ionizing, penetrating rays by certain atoms. Experiments conducted by British physicist Ernest Rutherford in 1899 showed that radioactive substances emit more than one kind of radiation.
Radioactivity - Natural, Artificial, Decay | Britannica
Sep 24, 2024 · Radioactivity - Natural, Artificial, Decay: Some species of radioactivity occur naturally on Earth. A few species have half-lives comparable to the age of the elements (about 6 × 109 years), so that they have not decayed away after their formation in stars.
Radiation | Definition, Types, Effects, & Facts | Britannica
Nov 4, 2024 · Radiation may be thought of as energy in motion either at speeds equal to the speed of light in free space—approximately 3 × 10 10 centimetres (186,000 miles) per second—or at speeds less than that of light but appreciably greater than thermal velocities (e.g., the velocities of molecules forming a sample of air). The first type constitutes the spectrum of electromagnetic radiation that ...
Radioactivity - Medical, Industrial, Research | Britannica
Sep 24, 2024 · Radioactivity - Medical, Industrial, Research: Radioisotopes have found extensive use in diagnosis and therapy, and this has given rise to a rapidly growing field called nuclear medicine. These radioactive isotopes have proven particularly effective as tracers in certain diagnostic procedures.
radioactivity - Kids | Britannica Kids | Homework Help
Radioactivity is a feature of certain types of matter. All matter is made of chemical elements, and elements are made of atoms. Most atoms are stable. That is, they do not change over time. Radioactive atoms, however, do change over time. Small particles and energy fly …
Radioactivity - Beta Decay, Nuclear Reactions, Radiation | Britannica
Sep 24, 2024 · Radioactivity - Beta Decay, Nuclear Reactions, Radiation: The processes separately introduced at the beginning of this section as beta-minus decay, beta-plus decay, and orbital electron capture can be appropriately treated together.
Radioactivity - Calculation, Measurement, Energy | Britannica
Sep 24, 2024 · Radioactivity - Calculation, Measurement, Energy: By the method of closed energy cycles, it is possible to use measured radioactive-energy-release (Q) values for alpha and beta decay to calculate the energy release for unmeasured transitions.
Henri Becquerel | French Physicist & Radioactivity Pioneer
Henri Becquerel was a French physicist who discovered radioactivity through his investigations of uranium and other substances. In 1903 he shared the Nobel Prize for Physics with Pierre and Marie Curie.
Half-life | Definition & Facts | Britannica
half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half.