Definition of "radium" [ra•di•um]

• A rare, brilliant white, luminescent, highly radioactive metallic element found in very small amounts in uranium ores, having 13 isotopes with mass numbers between 213 and 230, of which radium 226 with a half-life of 1,622 years is the most common. It is used in cancer radiotherapy, as a neutron source for some research purposes, and as a constituent of luminescent paints. Atomic number 88; melting point 700°C; boiling point 1,737°C; valence 2. See Table at element. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Slowly the uranium changes into radium, the radium changes into a gas called the radium emanation, and that again to what we call radium A, and so the process goes on, giving out energy at every stage, until at last we reach the last stage of all, which is, so far as we can tell at present, lead."
• "Having previously identified a new radioactive element, which they named polonium in honor of Marie's Polish origins, they have stumbled upon a second, which they called radium."
• "In 1911, a protocol for trade in radium preparations and a provisional plan for the function of the Radiumstation at the Allgemeines Krankenhaus were signed at the Radium Institute. 54 Shortly afterwards and on several occasions, radium was prepared at the Radium"