radium

[rey-dee-uhm]
noun
1.
Chemistry. a highly radioactive metallic element whose decay yields radon gas and alpha rays. Symbol: Ra; atomic weight: 226; atomic number: 88.
2.
a lustrous rayon or silk fabric constructed in plain weave and used in women's apparel, lining, and drapery.

Origin:
1895–1900; < Neo-Latin, equivalent to Latin rad(ius) ray (see radius) + -ium -ium

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World English Dictionary
radium (ˈreɪdɪəm)
 
n
a.  a highly radioactive luminescent white element of the alkaline earth group of metals. It occurs in pitchblende, carnotite, and other uranium ores, and is used in radiotherapy and in luminous paints. Symbol: Ra; atomic no: 88; half-life of most stable isotope, 226Ra: 1620 years; valency: 2; relative density: 5; melting pt: 700°C; boiling pt: 1140°C
 b.  (as modifier): radium needle
 
[C20: from Latin radius ray]

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Etymonline
Word Origin & History

radium
"radioactive metallic element," 1899, from Fr. radium (P. Curie et al., 1898), formed in Mod.L. from L. radius "ray" (see radius); so called for its power of emitting energy in the form of rays.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

radium ra·di·um (rā'dē-əm)
n.
Symbol Ra
A luminescent, highly radioactive metallic element found in minute amounts in uranium ores, used as a neutron source for some research purposes, and formerly used in cancer radiotherapy; its most stable isotope is Ra 226 with a half-life of 1,622 years. Atomic number 88; melting point 700°C; boiling point 1,140°C; valence 2.

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Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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American Heritage
Science Dictionary
radium   (rā'dē-əm)  Pronunciation Key 
Symbol Ra
A rare, bright-white, highly radioactive element of the alkaline-earth group. It occurs naturally in very small amounts in ores and minerals containing uranium, and it is naturally luminescent. Radium is used as a source of radon gas for the treatment of disease and as a neutron source for scientific research. Its most stable isotope is Ra 226 with a half-life of 1,622 years. Atomic number 88; melting point 700°C; boiling point 1,737°C; valence 2. See Periodic Table.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary

radium definition


A naturally occurring radioactive chemical element. Its symbol is Ra.

Note: Radium was discovered by the chemists Marie and Pierre Curie.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Example sentences
If you have old-fashioned luminous dials on your clocks they were made using
  radium, the glow was radiation.
Discovered that uranium emits radiation naturally, and isolated two new
  radioactive elements-polonium and radium.
Or all the radium poisonings back when radiation was fashionable.
In her work, she established the nature of radiation and beta rays, and
  discovered and isolated polonium and radium.
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