- a naturally occurring radioactive isotope of thorium. Symbol: Io; atomic number: 90; atomic weight: 230.
Origin of ionium
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for ionium
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
- obsolete a naturally occurring radioisotope of thorium with a mass number of 230Symbol: Io
C20: from New Latin, from ion + -ium