actinium

Meanings

1. 1
   noun

   the radioactive metallic chemical element with symbol Ac and atomic number 89, the first element of the actinide series

   Actinium occurs naturally in trace amounts in uranium ores and has no stable isotopes.

Borrowed from French actinium, named by André-Louis Debierne from Greek aktis, genitive aktinos ("ray, beam") + -ium in reference to the element's radioactivity. Actinium later gave its name to the actinide series.

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