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radium    音标拼音: [r'ediəm]
n. 镭



radium
n 1: an intensely radioactive metallic element that occurs in
minute amounts in uranium ores [synonym: {radium}, {Ra},
{atomic number 88}]

Radium \Ra`di*um\ (r[=a]"d[i^]*[u^]m), 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 is divalent, resembling barium
chemically. The main isotope of radium found in pitchblende,
radium-226, has a half-life of 1620 years, decaying first by
alpha emission to {radon}.

Note: 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). The beta and gamma rays seen in radium
preparations are in fact due to disintegration of decay
products of radium rather than the radium itself. 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 due to an inherent
instability of the atomic nucleus which causes its
decay in a process whose rate is first order. The
disintegration of the radium nucleus is only the first
in a series of nuclear disintegrations leading to
production of a series of elements and isotopes. The
chain has at least seven stages; the successive main
products have been studied and are {radon}, a gaseous
radioactive element belonging chemically to the inert
noble gas series (originally called radium emanation or
exradio, radium A, radium B, radium C, etc. The
successive products are unstable isotopes of several
different elements, each with an atomic weight a little
lower than its predecessor. Lead is the stable end
product. At the same time, the light gas helium is
formed, being generated when the expelled alpha
particles (positively charged helium nuclei) acquire
electrons. Radium, in turn, is formed in the
pitchblende ore by a slow disintegration of uranium.
Natural radium and also an isotope (radium-228, also
called mesothorium I) formed by the decay of thorium,
were at one time used to make a luminous paint for
watch dials, until the danger of the radioactivity
became fully appreciated, and use of such material in
watches was discontinued. See also {mesothorium}.
[Webster 1913 Suppl. PJC]

45 Moby Thesaurus words for "radium":
acid, actual cautery, americium, astatine, atomic cocktail,
berkelium, brand, brand iron, branding iron, caustic, cauter,
cauterant, cauterizer, cautery, cobalt, corrosive, curium,
einsteinium, electrocautery, escharotic, fermium, francium,
hahnium, hot iron, lunar caustic, mendelevium, mordant, moxa,
neptunium, plutonium, polonium, potential cautery, promethium,
protactinium, radiocalcium, radiocarbon, radioelement, radioiodine,
radioisotope, radiosodium, radon, tagged element, technetium,
tracer, uranium

radium
Symbol: Ra
Atomic number: 88
Atomic weight: (226)
Radioactive metallic transuranic element, belongs to group 2 of the
periodic table. Most stable isotope, Ra-226 has a half-life of 1602
years,
which decays into radon. Isolated from pitchblende in 1898 Marie and
Pierre Curie.


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  • Radium | Description, Properties, Symbol, Uses, Facts | Britannica
    Radium is a silvery white metal that does not occur free in nature Its most characteristic property is its intense radioactivity, which causes compounds of the element to display a faint bluish glow in the dark
  • Facts About Radium - Live Science
    Radium is a highly radioactive element and can be extremely dangerous However, it was once used in many everyday products, including wristwatches and toothpaste, and thought to have
  • Radium | NRC. gov
    Radium is a radioactive substance found in nature Radium is produced by the radioactive decay of uranium The intensity of radiation from radioactive materials decreases over time The time required for the intensity to decrease by one-half is referred to as the half-life The half-life of radium is approximately 1,600 years How is radium used?
  • Radium Facts, Symbol, Discovery, Properties, Uses - Chemistry Learner
    What is Radium A highly radioactive and naturally-occurring metal, radium (pronounced as RAY-dee-em) is formed when uranium and thorium undergo disintegration in the environment Represented by the chemical symbol Ra, it is classified in the family of alkaline earth metals [1]
  • Radium Element | History, Uses, Facts, Physical Chemical Characteristics
    Radium is silvery, lustrous, soft and radioactive element Its atomic symbol Ra, atomic number 88, atomic weight 226, solid at room temperature Melting point 700 C and boiling point 1140 C It is 6 th element in group 2 of periodic table Radium has density 5 5g cm 3 higher than barium
  • Radium Facts – Element 88 Symbol Ra - Science Notes and Projects
    Radium is a chemical element with the symbol Ra and atomic number 88 It is an alkaline earth metal and is the heaviest of the alkaline earth metals Radium was discovered in 1898 by Marie and Pierre Curie from a uranium ore called pitchblende
  • Radium - Element information, properties and uses | Periodic Table
    Element Radium (Ra), Group 2, Atomic Number 88, s-block, Mass [226] Sources, facts, uses, scarcity (SRI), podcasts, alchemical symbols, videos and images Jump to main content
  • Radium (Ra) - Definition, Preparation, Properties, Uses, Compounds . . .
    Radium is a radioactive chemical element with the symbol Ra and atomic number 88 It’s a heavy, silvery-white metal, part of the alkaline earth metal group, and is highly radioactive Discovered by Marie and Pierre Curie in 1898, radium emanates a faint blue glow, a property that has historically fascinated scientists and the public alike
  • Radium (Ra) - Periodic Table
    Radium is the 88th element in the periodic table and has a symbol of Ra and atomic number of 88 It has an atomic weight of (226) and a mass number of 201 Radium has eighty-eight protons and one hundred thirteen neutrons in its nucleus, and eighty-eight electrons in seven shells
  • Radionuclide Basics: Radium - US EPA
    Radium (chemical symbol Ra) is a naturally occurring radioactive element The most common isotopes of radium are radium-226 and radium-228





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