| slovo | definícia |
radium
(encz) | radium,radium n: [chem.] Zdeněk Brož |
radium
(czen) | radium,Ra[zkr.] [chem.] Michal Ambrož |
radium
(czen) | radium,radiumn: [chem.] Zdeněk Brož |
Radium
(gcide) | 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] |
radium
(wn) | radium
n 1: an intensely radioactive metallic element that occurs in
minute amounts in uranium ores [syn: radium, Ra,
atomic number 88] |
radium
(devil) | RADIUM, n. A mineral that gives off heat and stimulates the organ
that a scientist is a fool with.
|
radium
(elements) | 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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| | podobné slovo | definícia |
radium
(encz) | radium,radium n: [chem.] Zdeněk Brož |
radium
(czen) | radium,Ra[zkr.] [chem.] Michal Ambrožradium,radiumn: [chem.] Zdeněk Brož |
Osphradium
(gcide) | Osphradium \Os*phra"di*um\, n.; pl. Osphradia. [NL., fr. Gr. ?
strong scent, fr. ? to smell.] (Zool.)
The olfactory organ of some Mollusca. It is connected with
the organ of respiration.
[1913 Webster] Osprey |
radium emanation
(gcide) | Radon \Ra"don\ (r[=a]"d[o^]n), n. (Chem.)
An intensely radioactive gaseous element produced by the
radioactive decay of radium-226, which is the main isotope of
radium found in pitchblende. Chemically it is an inert noble
gas. Its atomic symbol is Rn. It has an atomic number of 86.
The radon isotope produced by decay of radium has an atomic
weight of 222.017, and this isotope decays by alpha emission
with a half-life of 3.82 days. Numerous other isotopes have
been observed, all radioactive and all having half-lives
shorter than that of radon-222. Radon was discovered by M.
and Mme. Curie, of Paris, in their studies of the radioactive
substances in pitchblende. Radon was originally called
radium emanation or exradio.
[PJC] |
radium F
(gcide) | Polonium \Po*lo"ni*um\ (p[-o]*l[=o]"n[i^]*[u^]m), n. [NL. So
named after Poland, in L. form Polonia, one of the
discoverers being a Pole.] (Chem.)
A radioactive chemical element, discovered by M. and MMe.
Curie in pitchblende, and originally called radium F. It
has atomic number 84 and an atomic weight of 210. It is a
very rare natural element, having an abundance in uranium
ores only 0.2% that of radium. It is closely related
chemically to bismuth. It emits only alpha rays, and has a
half-life of 138 days. It is thus more unstable than radium,
and a milligram of polonium emits as many alpha particles as
5 grams of radium. Twenty-seven isotopes are known, with
atomic masses from 192 to 218. At present a more practical
method of preparation than isolation from ores is the
preparation by neutron bombardment of bismuth in a nuclear
reactor, and it may be obtained commercially by users having
an appropriate permit. --[HBCF61]
[Webster 1913 Suppl. +PJC] |
radium
(wn) | radium
n 1: an intensely radioactive metallic element that occurs in
minute amounts in uranium ores [syn: radium, Ra,
atomic number 88] |
radium therapy
(wn) | radium therapy
n 1: the use of radium in radiation therapy [syn: {radium
therapy}, Curietherapy] |
radium
(devil) | RADIUM, n. A mineral that gives off heat and stimulates the organ
that a scientist is a fool with.
|
radium
(elements) | 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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