actinium

American  

[ak-tin-ee-uhm] / ækˈtɪn i əm /

noun

Chemistry.

1. a radioactive silver-white metallic element that glows blue in the dark, resembling the rare earths in chemical behavior and valence. Ac; 89; 227.

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actinium British  

/ ækˈtɪnɪəm /

noun

1. a radioactive element of the actinide series, occurring as a decay product of uranium. It is used as an alpha-particle source and in neutron production. Symbol: Ac; atomic no: 89; half-life of most stable isotope, ²²⁷ Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C

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actinium Scientific  

/ ăk-tĭn′ē-əm /

1. A silvery-white, highly radioactive metallic element of the actinide series that is found in uranium ores. It is about 150 times more radioactive than radium and is used as a source of alpha rays and neutrons. Its most stable isotope has a half-life of about 22 years. Atomic number 89; melting point 1,050°C (1,922°F); boiling point (estimated) 3,200°C (5,792°F); specific gravity (calculated) 10.07; valence 3.

2. See Periodic Table

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Etymology

Origin of actinium

First recorded in 1900–05; actin- + -ium

Example Sentences

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.

From Science Magazine • Aug. 26, 2021

Similarly, the behavior of actinium means it is part of the actinide series, although its electron configuration makes it the first member of the fourth transition series.

From Textbooks • Feb. 14, 2019

Nature Magazine reported Minder’s findings in an abstract by announcing that he had succeeded in isolating element 85 and that he had done so from the decomposition of the radioactive element actinium.

From Scientific American • Jul. 5, 2013

Of the three standard radioactive progressions � uranium-radium, actinium and thorium�those of uranium and thorium are the most alike.

From Time Magazine Archive

Similarly, by taking advantage of chemical relationship to the iron group of elements, another body was partially separated by Debierne, to which he gave the name actinium.

From A Brief Account of Radio-activity by Venable, Francis Preston