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ionium

[ahy-oh-nee-uh m]
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noun Chemistry.
  1. a naturally occurring radioactive isotope of thorium. Symbol: Io; atomic number: 90; atomic weight: 230.
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Origin of ionium

First recorded in 1905–10; ion + -ium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for ionium

Historical Examples

  • Ionium expels an alpha particle and becomes radium, which is a bivalent element resembling barium belonging to the second group.

    A Brief Account of Radio-activity

    Francis Preston Venable


British Dictionary definitions for ionium

ionium

noun
  1. obsolete a naturally occurring radioisotope of thorium with a mass number of 230Symbol: Io
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Word Origin

C20: from New Latin, from ion + -ium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012