actinium

radium${\displaystyle \longleftarrow }$ 89 ${\displaystyle \longrightarrow }$thorium

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Actinium

Pronunciation

• enPR: ăktĭn'ēəm, IPA ^(key): /ækˈtɪniəm/

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Noun

Singular actinium

Plural none

1. (uncountable) Actinium is a radioactive element with an atomic number of 89 and symbol Ac.