-
- To save this word, you'll need to log in.
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
Examples of actinium in a Sentence
Recent Examples on the Web
Those protons smashing and staying put creates the right kind of actinium through a process called spallation.
—
Sarah Scoles, Scientific American, 13 Feb. 2024
For years, scientists have produced this species of actinium by waiting for thorium (element 90, with one extra proton than actinium) to decay.
—
Sarah Scoles, Scientific American, 13 Feb. 2024
The lanthanide and actinide series — those two rows floating by themselves, named after their first members, lanthanum and actinium — are isolated like that as a concession to limited space.
—
Bill Andrews, Discover Magazine, 26 June 2019
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
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'actinium.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Word History
Dictionary Entries Near actinium
Cite this Entry
“Actinium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/actinium. Accessed 10 Jun. 2024.
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
More from Merriam-Webster on actinium
Britannica.com: Encyclopedia article about actinium
Love words? Need even more definitions?
Merriam-Webster unabridged
Share