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Any of a series of chemically similar, radioactive elements with atomic numbers ranging from 89 (actinium) through 103 (lawrencium). Also called actinoid.
(Elements & Compounds) a member of the actinide series. Also called: actinon
[C19: from actino- + -ide]
any element of the actinide series.
Any of a series of chemically similar metallic elements with atomic numbers ranging from 89 (actinium) to 103 (lawrencium). All of these elements are radioactive, and two of the elements, uranium and plutonium, are used to generate nuclear energy. See Periodic Table.