Hypertext Webster Gateway: "radium"
From Webster's Revised Unabridged Dictionary (1913) (web1913)
Radium \Ra`di*um\, n. [NL., fr. L. radius ray.] (Chem.)
An intensely radioactive metallic element found (combined) in
minute quantities in pitchblende, and various other uranium
minerals. Symbol, Ra; atomic weight, 226.4. Radium was
discovered by M. and Mme. Curie, of Paris, who in 1902
separated compounds of it by a tedious process from
pitchblende. Its compounds color flames carmine and give a
characteristic spectrum. It resembles barium chemically.
Radium preparations are remarkable for maintaining themselves
at a higher temperature than their surroundings, and for
their radiations, which are of three kinds: alpha rays, beta
rays, and gamma rays (see these terms). By reason of these
rays they ionize gases, affect photographic plates, cause
sores on the skin, and produce many other striking effects.
Their degree of activity depends on the proportion of radium
present, but not on its state of chemical combination or on
external conditions.The radioactivity of radium is therefore
an atomic property, and is explained as result from a
disintegration of the atom. This breaking up occurs in at
least seven stages; the successive main products have been
studied and are called
{radium emanation} or exradio,
{radium A},
{radium B},
{radium C}, etc. (The emanation is a heavy gas, the later
products are solids.) These products are regarded as
unstable elements, each with an atomic weight a little
lower than its predecessor. It is possible that lead is
the stable end product. At the same time the light gas
helium is formed; it probably consists of the expelled
alpha particles. The heat effect mentioned above is
ascribed to the impacts of these particles. Radium, in
turn, is believed to be formed indirectly by an
immeasurably slow disintegration of uranium.
From WordNet (r) 1.7 (wn)
radium
n : an intensely radioactive metallic element that occurs in
minute amounts in uranium ores [syn: {Ra}, {atomic number
88}]
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