Definition of ionium in English:

ionium

noun

Chemistry
  • A radioactive isotope of thorium with mass number 230, produced by the alpha decay of uranium-234 and decaying in turn to radium-226 with a half-life of 75,000 years. Symbols Io, 230Th.

Origin

Early 20th century. From ion + -ium. With the semantic motivation, compare quot. 1907.

Pronunciation

ionium

/ʌɪˈəʊnɪəm/