ac·tin·i·um
| \ ak-ˈti-nē-əm
\
\
Definition of actinium
: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende — see Chemical Elements Table
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“Actinium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/actinium. Accessed 28 Feb. 2021.
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actinium
noun
ac·tin·i·um
| \ ak-ˈtin-ē-əm
\
\
Medical Definition of actinium
: a radioactive trivalent metallic element that resembles lanthanum in chemical properties and that is found especially in pitchblende
—symbol Ac
— see Chemical Elements Table
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Time Traveler for actinium
The first known use of actinium was in 1900
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