actinium

radium$\longleftarrow$ 89 $\longrightarrow$thorium

Pronunciation

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

• Audio (UK)

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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.