| actinoid | Having the form of rays; radiated, as an actinia. Origin: Gr, ray. Source: Websters Dictionary (01 Mar 1998) |
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| metals, actinoid | A series of radioactive elements from actinium, atomic number 89, to and including lawrencium, atomic number 103. They are the theoretical analogs of the rare earth metal series. (12 Dec 1998) |
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