| slovo | definícia |
thorium
(encz) | thorium,thorium n: Zdeněk Brož |
thorium
(czen) | thorium,thoriumn: Zdeněk Brož |
Thorium
(gcide) | Thorium \Tho"ri*um\, n. [NL. See Thorite.] (Chem.)
A metallic element found in certain rare minerals, as
thorite, pyrochlore, monazite, etc., and isolated as an
infusible gray metallic powder which burns in the air and
forms thoria; -- formerly called also thorinum. Symbol Th.
Atomic weight 232.0.
[1913 Webster] |
thorium
(wn) | thorium
n 1: a soft silvery-white tetravalent radioactive metallic
element; isotope 232 is used as a power source in nuclear
reactors; occurs in thorite and in monazite sands [syn:
thorium, Th, atomic number 90] |
thorium
(elements) | thorium
Symbol: Th
Atomic number: 90
Atomic weight: 232.038
Grey radioactive metallic element. Belongs to actinoids. Found in
monazite sand
in Brazil, India and the US. Thorium-232 has a half-life of 1.39x10^10
years.
Can be used as a nuclear fuel for breeder reactors. Thorium-232 captures
slow
neutrons and breeds uranium-233. Discovered by Jons J. Berzelius in
1829.
|
| | podobné slovo | definícia |
radiothorium
(encz) | radiothorium, n: |
thorium-228
(encz) | thorium-228, n: |
Mesothorium
(gcide) | Mesothorium \Mes`o*tho"ri*um\, n. [NL.; meso- + thorium.]
(Chem.)
a radioactive isotope of radium (radium-228) with a half-life
of 5.8 years. Also called mesothorium-1 or mesothorium I
to distinguish it from a subsequent decay product,
mesothorium II (actinium-228). It was discovered in 1907 by
Otto Hahn as a decay product of thorium (produced by decay of
thorium-232). Mesothorium-1 (radium-228) in turn produces
actinium-228 (mesothorium-2) as the first product of its
radioactive decay, and the actinium-228 in turn decays
quickly (half-life of 6 hours) to thorium-228 (which is also
called radiothorium; the thorium-228 has a half-life of
1.91 years, shorter than that of the radium-228). It was
discovered and named before full recognition of the nature of
isotopes of the elements, and was distinguished from other
variants of radium by its half-life and mode of production
and decay. It was also cheaper to prepare than other
short-lived radium isotopes, and was thus sold commercially,
for use, e.g. in making watch dials readable in the dark by
painting the hands and hour marks with a self-luminous paint
containing the radioactive substance; it is therefore often
referred to (e.g. in regulatory legislation) as though
distinct from radium. It was one of the isotopes believed
responsible for radiation-induced diseases observed in
industrial workers who painted radium on watch dials in the
late 1950's and early 1960's. The primary isotope of radium
(radium-226) has a half-life of 1620 years, and these
isotopes with shorter half-lives proved difficult to isolate
and study for the purpose of finding the cause of such
diseases.
[Webster 1913 Suppl. +PJC] |
mesothorium I
(gcide) | Mesothorium \Mes`o*tho"ri*um\, n. [NL.; meso- + thorium.]
(Chem.)
a radioactive isotope of radium (radium-228) with a half-life
of 5.8 years. Also called mesothorium-1 or mesothorium I
to distinguish it from a subsequent decay product,
mesothorium II (actinium-228). It was discovered in 1907 by
Otto Hahn as a decay product of thorium (produced by decay of
thorium-232). Mesothorium-1 (radium-228) in turn produces
actinium-228 (mesothorium-2) as the first product of its
radioactive decay, and the actinium-228 in turn decays
quickly (half-life of 6 hours) to thorium-228 (which is also
called radiothorium; the thorium-228 has a half-life of
1.91 years, shorter than that of the radium-228). It was
discovered and named before full recognition of the nature of
isotopes of the elements, and was distinguished from other
variants of radium by its half-life and mode of production
and decay. It was also cheaper to prepare than other
short-lived radium isotopes, and was thus sold commercially,
for use, e.g. in making watch dials readable in the dark by
painting the hands and hour marks with a self-luminous paint
containing the radioactive substance; it is therefore often
referred to (e.g. in regulatory legislation) as though
distinct from radium. It was one of the isotopes believed
responsible for radiation-induced diseases observed in
industrial workers who painted radium on watch dials in the
late 1950's and early 1960's. The primary isotope of radium
(radium-226) has a half-life of 1620 years, and these
isotopes with shorter half-lives proved difficult to isolate
and study for the purpose of finding the cause of such
diseases.
[Webster 1913 Suppl. +PJC] |
mesothorium-1
(gcide) | Mesothorium \Mes`o*tho"ri*um\, n. [NL.; meso- + thorium.]
(Chem.)
a radioactive isotope of radium (radium-228) with a half-life
of 5.8 years. Also called mesothorium-1 or mesothorium I
to distinguish it from a subsequent decay product,
mesothorium II (actinium-228). It was discovered in 1907 by
Otto Hahn as a decay product of thorium (produced by decay of
thorium-232). Mesothorium-1 (radium-228) in turn produces
actinium-228 (mesothorium-2) as the first product of its
radioactive decay, and the actinium-228 in turn decays
quickly (half-life of 6 hours) to thorium-228 (which is also
called radiothorium; the thorium-228 has a half-life of
1.91 years, shorter than that of the radium-228). It was
discovered and named before full recognition of the nature of
isotopes of the elements, and was distinguished from other
variants of radium by its half-life and mode of production
and decay. It was also cheaper to prepare than other
short-lived radium isotopes, and was thus sold commercially,
for use, e.g. in making watch dials readable in the dark by
painting the hands and hour marks with a self-luminous paint
containing the radioactive substance; it is therefore often
referred to (e.g. in regulatory legislation) as though
distinct from radium. It was one of the isotopes believed
responsible for radiation-induced diseases observed in
industrial workers who painted radium on watch dials in the
late 1950's and early 1960's. The primary isotope of radium
(radium-226) has a half-life of 1620 years, and these
isotopes with shorter half-lives proved difficult to isolate
and study for the purpose of finding the cause of such
diseases.
[Webster 1913 Suppl. +PJC] |
radiothorium
(gcide) | radiothorium \ra`di*o*tho"ri*um\
(r[=a]`d[i^]*[o^]*th[^o]r"[=e]*[u^]m), n. (Chem.)
an earlier name for the thorium isotope thorium-228, given
by its discoverer Otto Hahn. It is a radioactive substance
formed as one of series of products in the chain of
radioactive decay of thorium. Its immediate predecessor in
the chain is Actinium-228, and it decays by alpha emission to
radium-224 with a half-life of 1.91 years. The name
radiothorium was given prior to the full understanding of the
nature of isotopes of elements.
[PJC] |
Thorium
(gcide) | Thorium \Tho"ri*um\, n. [NL. See Thorite.] (Chem.)
A metallic element found in certain rare minerals, as
thorite, pyrochlore, monazite, etc., and isolated as an
infusible gray metallic powder which burns in the air and
forms thoria; -- formerly called also thorinum. Symbol Th.
Atomic weight 232.0.
[1913 Webster] |
thorium-228
(gcide) | radiothorium \ra`di*o*tho"ri*um\
(r[=a]`d[i^]*[o^]*th[^o]r"[=e]*[u^]m), n. (Chem.)
an earlier name for the thorium isotope thorium-228, given
by its discoverer Otto Hahn. It is a radioactive substance
formed as one of series of products in the chain of
radioactive decay of thorium. Its immediate predecessor in
the chain is Actinium-228, and it decays by alpha emission to
radium-224 with a half-life of 1.91 years. The name
radiothorium was given prior to the full understanding of the
nature of isotopes of elements.
[PJC] |
radiothorium
(wn) | radiothorium
n 1: radioactive isotope of thorium with mass number 228 [syn:
thorium-228, radiothorium] |
thorium-228
(wn) | thorium-228
n 1: radioactive isotope of thorium with mass number 228 [syn:
thorium-228, radiothorium] |
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