| slovo | definícia |
actinium
(encz) | actinium,aktinium n: [chem.] macska |
Actinium
(gcide) | Actinium \Ac*tin"i*um\, n. [Gr. ?, ?, ray.] (Chem.)
A supposed metal, said by Phipson to be contained in
commercial zinc; -- so called because certain of its
compounds are darkened by exposure to light.
[1913 Webster] |
actinium
(wn) | actinium
n 1: a radioactive element of the actinide series; found in
uranium ores [syn: actinium, Ac, atomic number 89] |
actinium
(elements) | actinium
Symbol: Ac
Atomic number: 89
Atomic weight: (227)
Silvery radioactive metallic element, belongs to group 3 of the periodic
table. The most stable isotope, Ac-227, has a half-life of 217 years.
Ac-228 (half-life of 6.13 hours) also occurs in nature. There are 22
other
artificial isotopes, all radioactive and having very short half-lives.
Chemistry similar to lanthanum. Used as a source of alpha particles.
Discovered by A. Debierne in 1899.
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| | podobné slovo | definícia |
protactinium
(encz) | protactinium,protaktinium n: Zdeněk Brož |
protoactinium
(encz) | protoactinium, n: |
Actinium
(gcide) | Actinium \Ac*tin"i*um\, n. [Gr. ?, ?, ray.] (Chem.)
A supposed metal, said by Phipson to be contained in
commercial zinc; -- so called because certain of its
compounds are darkened by exposure to light.
[1913 Webster] |
Protactinium
(gcide) | Protactinium \Protactinium\
The radioactive chemical element, of atomic number 91; Atomic
symbol Pa; at. wt. of longest-lived isotope, 231 (T1/2 =
32,500 yrs.) Also called brevium, Uranium X2 and UX2.
[PJC] |
protactinium
(wn) | protactinium
n 1: a short-lived radioactive metallic element formed from
uranium and disintegrating into actinium and then into lead
[syn: protactinium, protoactinium, Pa, {atomic number
91}] |
protoactinium
(wn) | protoactinium
n 1: a short-lived radioactive metallic element formed from
uranium and disintegrating into actinium and then into lead
[syn: protactinium, protoactinium, Pa, {atomic number
91}] |
protactinium
(elements) | protactinium
Symbol: Pa
Atomic number: 91
Atomic weight: (231)
Radioactive metallic element, belongs to the actinoids. The most stable
isotope, Pa-231 has a half-life of 2.43*10^4 years. At least 10 other
radioactive isotopes are known. No practical applications are known.
Discovered in 1917 by Lise Meitner and Otto Hahn.
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