Definition of isotope noun from the Oxford Advanced Learner's Dictionary



BrE BrE//ˈaɪsətəʊp//
; NAmE NAmE//ˈaɪsətoʊp//
(physics, chemistry) Molecules and matter
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one of two or more forms of a chemical element which have the same number of protons but a different number of neutrons in their atoms. They have different physical properties (= characteristics) but the same chemical ones radioactive isotopes the many isotopes of carbon See related entries: Molecules and matter Word Origin1913: coined by F. Soddy, from iso- ‘equal’ + Greek topos ‘place’ (because the isotopes occupy the same place in the periodic table of elements).
See the Oxford Advanced American Dictionary entry: isotope