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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.
Radiation, flow of atomic and subatomic particles and of waves, such as those that characterize heat rays, light rays, and X rays. All matter is constantly bombarded with radiation of both types from cosmic and terrestrial sources.
A radioactive isotope, also known as a radioisotope, radionuclide, or radioactive nuclide, is any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays. Every chemical element has one or more ...
Ionizing radiation, flow of energy in the form of atomic and subatomic particles or electromagnetic waves that is capable of freeing electrons from an atom, causing the atom to become charged (or ionized). Ionizing radiation includes the more energetic end of the electromagnetic spectrum and subatomic particles.
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 out of them naturally.
Half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay, or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half.
electromagnetic radiation, in classical physics, the flow of energy at the universal speed of light through free space or through a material medium in the form of the electric and magnetic fields that make up electromagnetic waves such as radio waves, visible light, and gamma rays.
A radioactive isotope, also known as a radioisotope, radionuclide, or radioactive nuclide, is any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays. Every chemical element has one or more ...
A gamma ray is electromagnetic radiation of the shortest wavelength and highest energy. Gamma-ray radiation has wavelengths generally smaller than a few tenths of an angstrom (10 −10 meter), and gamma-ray photons have energies greater than tens of thousands of electron volts.
nuclear energy, energy that is released in significant amounts in processes that affect atomic nuclei, the dense cores of atoms. It is distinct from the energy of other atomic phenomena such as ordinary chemical reactions, which involve only the orbital electrons of atoms.