A a


    • US Pronunciation
    • US IPA
    • [ak-tin-ee-uh m]
    • /ækˈtɪn i əm/
    • US Pronunciation
    • US IPA
    • [ak-tin-ee-uh m]
    • /ækˈtɪn i əm/

Definitions of actinium word

  • noun actinium 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,227Ac: 21.6 years; relative density: 10.07; melting pt: 1051°C; boiling pt: 3200 ± 300°C 3
  • noun actinium a white, radioactive, metallic chemical element, the first member of the actinide series, found in pitchblende and other minerals or formed in reactors by the neutron irradiation of radium: symbol, Ac; at. no., 89 3
  • noun actinium a radioactive silver-white metallic element that glows blue in the dark, resembling the rare earths in chemical behavior and valence. Symbol: Ac; atomic number: 89; atomic weight: 227. 1
  • noun actinium The chemical element of atomic number 89, a radioactive metallic element of the actinide series. It is rare in nature, occurring as an impurity in uranium ores. 1
  • noun actinium a radioactive, metallic chemical element (symbol: Ac) with an atomic number of 89; found in uranium ores. 0

Information block about the term

Origin of actinium

First appearance:

before 1900
One of the 17% newest English words
First recorded in 1900-05; actin- + -ium

Historical Comparancy

Parts of speech for Actinium


actinium popularity

A common word. It’s meaning is known to most children of preschool age. About 88% of English native speakers know the meaning and use the word.
This word is included in each student's vocabulary. Most likely there is at least one movie with this word in the title.

actinium usage trend in Literature

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Synonyms for actinium

noun actinium

  • ac — AC is used to refer to an electric current that continually changes direction as it flows. AC is an abbreviation for 'alternating current'.

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