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Definition: Isotope from Encyclopedia of Cancer
Definition

Isotope contains the atoms of a chemical element that differ only in the number of neutrons but not in the number of protons. Every element contains stable or instable (radioactive) isotopes. Hydrogen for instance has two isotopes: deuterium whose nucleus has one proton and one neutron and tritium whose nucleus has one proton and two neutrons.

See also Radiation Oncology; Radon

isotope

From The Columbia Encyclopedia
(ī'sӘtōp), in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F. Soddy in explaining aspects of radioactivity; the first stable isotope (of neon) was discovered by J. J. Thomson . The nuclei of isotopes contain identical numbers of protons, equal to the atomic number of the atom, and thus represent the same chemical element, but do not have the same number of neutrons. Thus isotopes of a given element have identical chemical properties but slightly different physical properties and very different half-lives, if they are radioactive (see half-life ). For most elements, both stable and radioactive isotopes are known. Radioactive isotopes of many common elements, such as carbon and phosphorus, are used as tracers in medical, biological, and industrial research. Their radioactive nature makes it possible to follow the substances in their paths through a plant or animal…
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Full text Article isotope

From The Columbia Encyclopedia
(ī'sӘtōp), in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F. Soddy in explaining aspects of radioactivity; the first stable isotope (of neon) was discovered by J. J. Thomson . …
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Full text Article isotope

From The Penguin Dictionary of Science
One of two or more atomic species having the same ➤ atomic number but different ➤ nucleon numbers . Isotopes are therefore variants of the same element as the number of protons is the same; however, the number of neutrons, and hence the mass of the atom, varies. For example, chlorine has two…
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Full text Article isotope

From Hawley's Condensed Chemical Dictionary
One of two or more forms or species of an element that have the same atomic number, i.e., the same position in the periodic table, but different masses. The difference in mass is due to the presence of one or more extra neutrons in the nucleus. Thus, “regular” hydrogen, with atomic number 1 and a…
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Full text Article isotope

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
One of two or more atoms that have the same atomic number (same number of protons), but which contain a different number of neutrons, thus differing in their relative atomic mass . They may be stable or radioactive (as a radioisotope ), naturally occurring, or synthesized. For example, hydrogen has…
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Full text Article isotopes

From The Penguin Dictionary of Physics
Two or more NUCLIDES that have an identical nuclear charge (i.e. the same atomic number) but differ in nuclear mass; the nuclides are said to be isotopic . Such substances have almost identical chemical properties but differing physical properties, and each is said to be an isotope of the element of…
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Full text Article Isotopes

From 50 Chemistry Ideas You Really Need to Know
Isotopes
Isotopes aren't just deadly substances used to make bombs and poison people. The concept of an isotope is one that encompasses many chemical elements that have a slightly altered quota of subatomic particles. Isotopes are present in the air we breathe and the water we drink. You can even use them…
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Full text Article Isotope

From Black's Medical Dictionary, 43rd Edition
This is a form of a chemical element with the same chemical properties as other forms, but which has a different atomic mass. It contains an identical number of positively charged particles called protons in the nucleus, giving it the same atomic number and thus identity as an element, but the…
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Beyond the analysis of the chemical elements in a sample of matter, it is possible to determine the isotopic content of the individual chemical elements. The chemical analysis of a substance generally takes its isotopic composition to be a “standard” that represents terrestrial composition, because…
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The three isotopes of carbon, showing...
Abstract Isotopes record human influence on the Earth System, providing evidence for the Anthropocene. Lead and sulfur isotopes detail pollution histories going back millennia. Carbon and nitrogen isotopes show substantial change since the Industrial Revolution, and especially since the 1950s, …
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Full text Article radioactive isotope

From The Columbia Encyclopedia
or radioisotope, natural or artificially created isotope of a chemical element having an unstable nucleus that decays, emitting alpha, beta, or gamma rays until stability is reached. The stable end product is a nonradioactive isotope of another element, i.e., radium-226 decays finally to lead-206. …
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