thorium

actinium${\displaystyle \longleftarrow }$ 90 ${\displaystyle \longrightarrow }$protactinium

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Thorium

Pronunciation

• enPR: thôr'ēəm, IPA ^(key): /ˈθɔːriəm/

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Noun

Singular thorium

Plural none

1. (uncountable) Thorium is a radioactive element with an atomic number of 90 and symbol Th.