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Definition of Radioactivity

Babylon English

emission of energy due to atomic decay, production of radiation as a result of atomic breakdown
Radioactivity Definition from Language, Idioms & Slang Dictionaries & Glossaries
hEnglish - advanced version

radioactivity
radium \ra`di*um\ (?), n. [nl., fr. l. radius ray.] (chem.) an intensely radioactive metallic element found (combined) in minute quantities in pitchblende, and various other uranium minerals. symbol, ra; atomic weight, 226.4. radium was discovered by m. and mme. curie, of paris, who in 1902 separated compounds of it by a tedious process from pitchblende. its compounds color flames carmine and give a characteristic spectrum. it resembles barium chemically. radium preparations are remarkable for maintaining themselves at a higher temperature than their surroundings, and for their radiations, which are of three kinds: alpha rays, beta rays, and gamma rays (see these terms). by reason of these rays they ionize gases, affect photographic plates, cause sores on the skin, and produce many other striking effects. their degree of activity depends on the proportion of radium present, but not on its state of chemical combination or on external conditions.the radioactivity of radium is therefore an atomic property, and is explained as result from a disintegration of the atom. this breaking up occurs in at least seven stages; the successive main products have been studied and are called


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 radioactivity unit 
WordNet 2.0

Noun
1. the spontaneous emission of a stream of particles or electromagnetic rays in nuclear decay
(synonym) radiation
(hypernym) emission
(hyponym) corpuscular radiation, particulate radiation
Radioactivity Definition from Business & Finance Dictionaries & Glossaries
Glossary of petroleum Industry
the property possessed by some substances (as radium, uranium, or thorium) of releasing alpha panicles, beta particles, or gamma particles as the substance spontaneously disintegrates.
Radioactivity Definition from Government Dictionaries & Glossaries
DOD Dictionary of Military Terms
The spontaneous emission of radiation, generally alpha or beta particles, often accompanied by gamma rays, from the nuclei of an unstable isotope.
  
Source: U.S. Department of Defense, Joint Doctrine Division. ( About )
Radioactivity Definition from Science & Technology Dictionaries & Glossaries
General Chemistry Glossary
Spontaneous emission of particles or high-energy electromagnetic radiation from the nuclei of unstable atoms. "Radiation" refers to the emissions, and "radioactive source" refers to the source of the radiation.
NRC Nuclear Energy Glossary
The spontaneous emission of radiation, generally alpha or beta particles, often accompanied by gamma rays, from the nucleus of an unstable isotope. Also, the rate at which radioactive material emits radiation. Measured in units of becquerels or disintegrations per second.

Radioactive Decay of an Atom
A service to the public by The U.S. Nuclear Regulatory Commission (NRC).
EIA Energy Glossary
The spontaneous emission of radiation from the nucleus of an atom. Radionuclides lose particles and energy through this process.
Source: Energy Information Administration, 2006
ASTRONOMY UNBOUND

The spontaneous disintegration of certain atomic nuclei by emission of either 2 protons bound with 2 neutrons (a helium nucleus), known as alpha decay , or of an electron, known as beta decay . If the emitted beta particle is the antimatter positive electron the disintegration process is termed positron emission. Radioactive decay is sometimes accompanied by the emission of gamma rays and is always accompanied by the transmutation of the atomic nucleus into another element which is more stable. The rate of decay, known as the halflife , together with the energy of the emitted particle, is unique to the radionuclide (the species of unstable nucleus).
Radioactivity Definition from Encyclopedia Dictionaries & Glossaries
Wikipedia English - The Free Encyclopedia
Radioactive decay, also known as nuclear decay or radioactivity, is the process by which a nucleus of an unstable atom loses energy by emitting particles of ionizing radiation. A material that spontaneously emits this kind of radiation—which includes the emission of energetic alpha particles, beta particles, and gamma rays—is considered radioactive.

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Radioactivity Definition from Entertainment & Music Dictionaries & Glossaries
English to Federation-Standard Golic Vulcan
galu-saya'es
Radioactivity Definition from Religion & Spirituality Dictionaries & Glossaries
Rakefet
Radioactivity Scientific discovery has done much to verify the occult axiom that there are no permanent bodies, but that everything is in a state of flux and interchange. Theosophy views the physical universe as an ocean of life, partly imbodied and partly noncorporeal, and regards such terms as matter, energy, wave, and particle as descriptive of various manifestations of this life. The chemical elements are now considered by science to be centers or vortices in a fluid ocean, continually giving and receiving emanations from each other. Thus all forms of physical matter emit radiation and radioactive phenomena are instances of a general law. The emanations studied by science are described partly as actinic rays and partly as emitted particles; and the disintegration series results in a continual emission of both these forms of emanation, accompanied by an elevation of the temperature of the radioactive body above that of its surroundings, a loss of its own mass, the formation of temporary unstable elements of lower atomic weight, until an end-product is reached. Calculations as to the age of the solid crust of the earth, based on disintegration rates, are extremely unreliable, as they involve unverified assumptions as to the rate of this process in past ages. Theosophy states that during the descending arc of cosmic evolution, the process of concretion is predominant, and during the ascending arc the process of disintegration or etherealization is predominant. This indicates that the rate of radioactive disintegration has been on the increase in comparatively recent times, and will continue at an enlarging rate into the geologic future.
Radioactivity Definition from Medicine Dictionaries & Glossaries
CDC Radiological Terms
 the process of spontaneous transformation of the nucleus, generally with the emission of alpha or beta particles often accompanied by gamma rays. This process is referred to as decay or disintegration of an atom.
  
the rate of decay of radioactive material expressed as the number of atoms breaking down per second measured in units called becquerels or curies.
  
Source: Centers for Disease Control and Prevention (CDC) ( About )