francium


francium
/fran"see euhm/, n. Chem.
a radioactive element of the alkali metal group. Symbol: Fr; at. no.: 87.
[1945-50; after FRANCE where first identified; see -IUM]

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 heaviest chemical element of Group 1 (Ia) in the periodic table, the alkali metal group. It exists only in short-lived radioactive forms. Natural francium cannot be isolated in visible, weighable amounts, for only 24.5 grams (0.86 ounce) occur at any time in the entire crust of Earth. The existence of francium was predicted by Russian chemist Dmitry I. Mendeleyev in his periodic classification of the elements. French chemist Marguerite Perey discovered francium (1939) while studying actinium-227, which decays by negative beta decay ( electron emission) to an isotope of thorium (thorium-227) and by alpha emission (about 1 percent) into an isotope of francium (francium-223) that was formerly called actinium K (AcK) and is a member of the actinium decay series. Though it is the longest-lived isotope of francium, francium-223 has a half-life of only 22 minutes. Nineteen isotopes of francium with masses between 204 and 224 have been artificially prepared, and, because natural francium cannot be concentrated, it is also prepared by neutron irradiation of radium to produce actinium, which decays to produce traces of francium. The chemistry of francium can be studied only by methods designed for trace quantities. In all respects, its observed behaviour, including the oxidation state of +1, is that to be expected of an alkali element filling a place just below cesium in the periodic table of the elements. There is almost no information on its biological aspects.

atomic number
87
stablest isotope
(223)
oxidation state
+1
electronic config.
2-8-18-32-18-8-1 or [Rn] 7s1
James L. Dye
 

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Universalium. 2010.

Look at other dictionaries:

  • Francium — Radon ← Francium → Radium Cs …   Wikipédia en Français

  • FRANCIUM — De France Symbole chimique: Fr Numéro atomique: 87. Dernier représentant des métaux alcalins dont la case dans le tableau périodique resta vacante jusqu’à 1939, quand Marguerite Perrey (Institut Curie à Paris) en découvrit un isotope radioactif… …   Encyclopédie Universelle

  • francium — FRÁNCIUM s.n. v. franciu. Trimis de LauraGellner, 13.09.2007. Sursa: DN …   Dicționar Român

  • francium — Symbol: Fr Atomic number: 87 Atomic weight: (223) Radioactive element, belongs to group 1 of the periodic table. Found in uranium and thorium ores. The 22 known isotopes are all radioactive, with the most stable being Fr 223. Its existence was… …   Elements of periodic system

  • francium — [fran′sē əm] n. [ModL < FRANCE2 + IUM] a radioactive chemical element, an alkali metal, existing in minute amounts in nature as a decay product of actinium: symbol, Fr; at. no., 87: see the periodic table of elements in the Reference… …   English World dictionary

  • Francium — radon ← francium → radium Cs ↑ Fr ↓ Uue …   Wikipedia

  • Francium — Eigenschaften …   Deutsch Wikipedia

  • Francium — Frạn|ci|um 〈n.; s; unz.; chem. 〉 radioaktives Alkalimetall, Ordnungszahl 87; oV Franzium [<nlat. Francia „Frankreich“ + lat. Endung ...ium] * * * Frạn|ci|um [frz. France =Frankreich; ↑ ium (1)], das; s; Symbol: Fr: äußerst seltenes,… …   Universal-Lexikon

  • Francium — francis statusas T sritis fizika atitikmenys: angl. francium; virginium vok. Francium, n rus. франций, m pranc. francium, m …   Fizikos terminų žodynas

  • francium — francis statusas T sritis fizika atitikmenys: angl. francium; virginium vok. Francium, n rus. франций, m pranc. francium, m …   Fizikos terminų žodynas


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