actinium

noun

ac·​tin·​i·​um ak-ˈti-nē-əm 

: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende see Chemical Elements Table

Example Sentences

Recent Examples on the Web

Other theorists have predicted that hydrides such as calcium hydride or actinium hydride should superconduct at close to room temperature—and at a pressure considerably less than that needed for CSH. Robert F. Service, Science | AAAS, 26 Aug. 2021

Word History

Etymology

borrowed from French, from Greek aktīn-, aktís "ray, beam" + -ium -ium; so called from its radioactivity — more at actin-

First Known Use

1900, in the meaning defined above

Kids Definition

actinium

noun

ac·​tin·​i·​um ak-ˈtin-ē-əm 

: a radioactive metallic element found especially in pitchblende see element

Medical Definition

actinium

noun

ac·​tin·​i·​um ak-ˈtin-ē-əm 

: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende

—symbol Ac see Chemical Elements Table