(Francium; from the name of France), Fr - radioactive chemical. element of group I of the periodic system of elements; at. n. 87. Has no stable isotopes. 18 radioactive isotopes with mass numbers from 204 to 224 and half-lives from 5 10 -3 sec (218Fr) to 23 min (212Fr) have been obtained. The existence of F. and some of his saints predicted (1870) Rus. scientist D. I. Mendeleev, calling the element unknown at the time as ekacesium. Ekacesium was discovered in 1939 by the French. researcher M. Perey in the study of the radioactive decay of actinium and named "actinium K". In 1949 actinium K was renamed francium. The isotopes 223Fr and 221Fr are found in nature, of which the 223Fr isotope is a product of the radioactive decay of actinium 227Ac. 1 m of natural uranium contains 0.2 mg of 227Ac and 3.8 10 -10 g of 223Fr. Francium is the heaviest element among the alkali metals. Atomic radius 12.83 A. Ionic radius Fr+ is 1.80 A. Density (temperature 20°C) 2.44 g/cm3; mp 20°C; t kip630 ° С; heat capacity 0.0338 cal/g-deg; electrical resistance (t-ra 18 C) 45 10-6 ohm-cm.
According to chem. St. Francium is a complete analogue of rubidium and cesium. Fluoride hydroxide, chloride, nitrate, sulfate, sulfide, carbonate, acetate, and F. oxalate dissolve well in water; perchlorate, picrate, iodate, chloroplatinate, chlorobismuthate, chloro-antimonate, chlorostannate and cobalt-tinitrite F., as well as double salt Fr9Bi2I9 and francium salts with heteropoly acids are poorly soluble in water. Francium is isolated by various methods from the decay products of 227Ac, from uranium resin ore, from the products of irradiation of thorium and uranium with fast protons, and also from the products of irradiation of gold with 22Ne ions. When F. is isolated from the decay products of 227Ac, an aqueous solution of actinium chloride is boiled with an excess of sodium carbonate, the precipitate is filtered off, hydrochloric acid is added to the filtrate and boiled again to destroy carbonate ions. Then small amounts of lanthanum and barium chloride, potassium and ammonium chromate are added. After that, the precipitate of chromates is filtered off, and the filtrate containing 223Fr is concentrated by evaporation. Francium is isolated from solutions containing, in addition to phosphorus salts, other compounds, using ion-exchange resins, electrophoresis, chromatography, and other methods. Francium is used to determine the presence of actinium in natural objects. The 223Fr isotope finds application in biological research.
Element characteristic
One thing is certain - its valence electron is at 7s -orbitals, and the radius of the atom is the largest among all elements of the periodic system. Francium is a radioactive chemical element. It has no stable isotopes, and those that are known are short-lived and quickly decay, emittingβ -radiation (electrons). On the whole globe it is hardly found ~ 500g.
Properties of a simple substance and compounds
All data on the properties of francium are obtained by extrapolation based on the results of coprecipitation with other elements. In chemical terms, I g is the closest analogue of cesium, in terms of francium it is even more electropositive. Its only stable oxidation state is +1.
Getting and using
Francium is obtained only in the form of its connection by separation from actinium. By ion-exchange separation on a resin column« Dowex-50" microscopic amount of 95% pure francium can be obtained. However, its half-life is 22 minutes, i.e., after each such interval, its amount is halved. Hasn't found any use yet. The radio emission of francium helps to find. Publications have appeared that state that the radioactivity of francium can be useful in the diagnosis of oncological diseases: it is selectively able to accumulate in tumors at the earliest stages of their development.
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Opening history:
Francium is one of four elements (Nos. 43, 61, 85 and 87) that remained undiscovered by 1925. The ecaesium predicted by Medeleev was sought as a companion of cesium in cesium minerals. From 1929 to 1939, eca-cesium was "found" several times, sometimes called virginium in honor of the US state, then moldavium, then alkalinium or russia. However, all these discoveries were wrong.
In 1939 Marguerite Perey from the Curie Institute in Paris, while purifying an actinium preparation (Ac-227) from a variety of radioactive decay products, discovered b-radiation that could not belong to any of the isotopes known at that time. When this isotope (half-life 21 min) was subjected to chemical analysis, it turned out that its properties corresponded to those of ecaesium.
This was finally confirmed after the Second World War, and in 1946 Perey proposed to name the new element Francium in honor of her homeland.
Receipt:
Francium-223 (the longest-lived isotope of francium, half-life 22.3 minutes) is one of the side branches of the natural radioactive uranium-235 series and is found in extremely small quantities in uranium minerals. Its formation from actinium can be expressed by the equation: 227 Ac (-, a) 223 Fr. According to estimates, its equilibrium content in the earth's crust is 340 g. Also, one of the side branches of the radioactive series of thorium contains francium-224 with a half-life of 3.0 minutes. Its equilibrium content in the earth's crust is only 0.5 g.
Other isotopes of francium are also obtained by nuclear reactions. One of the most common reactions: 197 Au + 18 O = 210 Fr + 5n
Physical properties:
radioactive metal. Due to the high radioactivity, studies are carried out with microscopic quantities. According to the latest data, the density of francium at room temperature is 1.87 g/cm 3 , melting point 27°C, boiling point 677°C.
France undergoes b-decay, turning into an isotope of radium: 223 Fr (-, b) 223Ra
Chemical properties:
Francium has the lowest electronegativity of any element currently known. Electrode potential Fr + /Fr = -2.92 V.
Accordingly, francium is also the most reactive alkali metal.
In compounds, it exhibits an oxidation state of +1.
The most important connections:
The compounds have been little studied due to the radioactivity of francium. It has most of the properties characteristic of other alkali metals, is most similar in properties to cesium, and always co-crystallizes with its compounds. So, to isolate francium from a mixture with other products of nuclear reactions, it is used based on its co-precipitation with insoluble cesium salts (cesium perchlorate or cesium silicotungstate). It is also extracted from solutions with cesium and rubidium chloroplatinates Cs 2 PtCl 6 and Rb 2 PtCl 6 , chlorobismuthate Cs 2 BiCl 5 , chlorostannate Cs 2 SnCl 6 and cesium chloroantimonate Cs 2 SbCl 5 2.5H 2 O, as well as free heteropoly acids - silicotungstic and phosphotungsten.
Forms soluble salts and hydroxide.
Application:
Francium chloride FrCl has been used to detect cancerous tumors, but due to the extremely high cost, this salt is unprofitable in large-scale developments.
Currently, francium and its salts have not yet been used, due to the short half-life and high radioactivity.
Testova Christina
HF Tyumen State University, 581 groups, 2011
Sources: Francius. Popular library of chemical elements http://n-t.ru/ri/ps/pb087.htm
France. Wikipedia, the free encyclopedia.
- (Francium), Fr, radioactive chemical element of group I of the periodic system, atomic number 87; alkali metal. France was discovered by the French radiochemist M. Pere in 1939 ... Modern Encyclopedia
FRANCE- (lat. Francium) Fr, a chemical element of group I of the periodic system of Mendeleev, atomic number 87, atomic mass 223.0197, belongs to alkali metals. Radioactive, the most stable isotope is 223Fr (half-life 21.8 min). Named after… Big Encyclopedic Dictionary
FRANCE- (symbol Fr), a radioactive, metallic element of the first group of the periodic table, discovered in 1939. The heaviest element of the alkali metal series. In its natural form, it is present in uranium ore, a decomposition product of ACTINIUM. Rare item... Scientific and technical encyclopedic dictionary
France- Fr (named in honor of France, the birthplace of M. Pepe, who discovered the element; lat. Francium * a. francium; n. Franzium; f. francium; and. francio, francium), radioactive chem. element of group I of the Mendeleev system; at. n. 87. Has no stable isotopes. ... ... Geological Encyclopedia
FRANCE- (lat. Francium), Fr, radioact. chem. element of the 1st group periodic. systems of elements, at. number 87, refers to the alkali metals. Naim. stable from all radioactive. elements found in nature. Natural F. consists of b radioactive 223Fr ... ... Physical Encyclopedia
francium- noun, number of synonyms: 2 metal (86) element (159) ASIS synonym dictionary. V.N. Trishin. 2013 ... Synonym dictionary
francium- I; cf. [lat. Francium] Chemical element (Fr), radioactive alkali metal. ◁ French, oh, oh. * * * Francium (lat. Francium), a chemical element of group I of the periodic system, belongs to the alkali metals. Radioactive, most stable ... ... encyclopedic Dictionary
FRANCE- (lat. Francium), chem. element I gr. periodic systems, refers to alkali metals. Radioactive, max. the nuclide 223Fr is stable (half-life 22 min). Name from France, the homeland of M. Perey, who discovered the element. One of the rarest and least... Natural science. encyclopedic Dictionary
France- See Francius (Fr) ... Encyclopedic Dictionary of Metallurgy
francium- francis statusas T sritis chemija apibrėžtis Cheminis elementas. simbolis(iai) Fr atitikmenys: lot. francium engl. francium rus. francium ... Chemijos terminų aiskinamasis žodynas
Books
- Radioactive metals francium and dubnium. Methods for predicting physical parameters, Nikolaev OS The book contains methods for predicting the physical parameters of francium and dubnium. These are radioactive metals of the seventh period of the table of D. I. Mendeleev. Short half-lives of these metals… Buy for 538 UAH (Ukraine only)
- De Gaulle and the Gaullists. "Constable" and his associates, Vladlen Maximov. The book tells about the most famous Frenchman of the 20th century, the founder and first president of the Fifth Republic, from an unusual and unexpected critical side for the Russian reader. The author details...
- (Francium), Fr, radioactive chemical element of group I of the periodic system, atomic number 87; alkali metal. France was discovered by the French radiochemist M. Pere in 1939 ... Modern Encyclopedia
- (lat. Francium) Fr, a chemical element of group I of the periodic system of Mendeleev, atomic number 87, atomic mass 223.0197, belongs to alkali metals. Radioactive, the most stable isotope is 223Fr (half-life 21.8 min). Named after… Big Encyclopedic Dictionary
- (symbol Fr), a radioactive, metallic element of the first group of the periodic table, discovered in 1939. The heaviest element of the alkali metal series. In its natural form, it is present in uranium ore, a decomposition product of ACTINIUM. Rare item... Scientific and technical encyclopedic dictionary
Fr (named in honor of France, the birthplace of M. Pepe, who discovered the element; lat. Francium * a. francium; n. Franzium; f. francium; and. francio, francium), radioactive chem. element of group I of the Mendeleev system; at. n. 87. Has no stable isotopes. ... ... Geological Encyclopedia
- (lat. Francium), Fr, radioact. chem. element of the 1st group periodic. systems of elements, at. number 87, refers to the alkali metals. Naim. stable from all radioactive. elements found in nature. Natural F. consists of b radioactive 223Fr ... ... Physical Encyclopedia
Exist., number of synonyms: 2 metal (86) element (159) ASIS synonym dictionary. V.N. Trishin. 2013 ... Synonym dictionary
I; cf. [lat. Francium] Chemical element (Fr), radioactive alkali metal. ◁ French, oh, oh. * * * Francium (lat. Francium), a chemical element of group I of the periodic system, belongs to the alkali metals. Radioactive, most stable ... ... encyclopedic Dictionary
- (lat. Francium), chem. element I gr. periodic systems, refers to alkali metals. Radioactive, max. the nuclide 223Fr is stable (half-life 22 min). Name from France, the homeland of M. Perey, who discovered the element. One of the rarest and least... Natural science. encyclopedic Dictionary
France- See Francius (Fr) ... Encyclopedic Dictionary of Metallurgy
francium- francis statusas T sritis chemija apibrėžtis Cheminis elementas. simbolis(iai) Fr atitikmenys: lot. francium engl. francium rus. francium ... Chemijos terminų aiskinamasis žodynas
Books
- Radioactive metals francium and dubnium. Methods for predicting physical parameters, Nikolaev OS The book contains methods for predicting the physical parameters of francium and dubnium. These are radioactive metals of the seventh period of the table of D. I. Mendeleev. The short half-lives of these metals...
- De Gaulle and the Gaullists. "Constable" and his associates, Vladlen Maximov. The book tells about the most famous Frenchman of the 20th century, the founder and first president of the Fifth Republic, from an unusual and unexpected critical side for the Russian reader. The author details...
Francium is an element with an atomic number of 87. The atomic mass of the longest-lived isotope is 223. Francium is a radioactive alkali metal, has an extremely pronounced chemical reactivity.
franciumThe history of the discovery of france
The metal was discovered back in 1939 by an employee of the Paris Radium Institute named Marguerite Perey. She, apparently out of patriotic feelings, named the element in honor of her homeland. Francium was discovered while studying the artificially obtained element "actinium": an uncharacteristic radioactive glow was noticed. For the sake of fairness, it should be noted that other researchers could work on the creation of this element at the same time as it, but, as they say, the winners are not judged.
Main characteristics
Today, francium is one of the rarest metals (and chemical elements in general) that are found in nature.
Earth's Crust
According to scientists, the content of this metal in the earth's crust is about 340 grams (only astatine is less). This is mainly due to its physical instability. Being radioactive, it has a very short half-life (the most stable isotope has a half-life of 22.3 minutes). The only thing that compensates for its natural content is that francium is an intermediate in the decay of uranium-235 and thorium-232. Thus, all francium, which is found in natural conditions, is a product of radioactive decay.
How can you get it?
Consider the only way to obtain the most stable francium isotope. This can be done by nuclear reaction of gold with oxygen atoms. All other methods (meaning radioactive decay) are inappropriate, since extremely unstable isotopes are obtained that “live” for no more than a few minutes. Obtaining this element at home, like all its compounds, of course, will not work (and there is no need, in fact). many experiments with other metals can be found.
What are the chemical properties of francium?
Francium is similar in properties to cesium. The relativistic effects of the 6p shell ensure that the bond between francium and oxygen in superoxides (for example, FrO 2 composition) is more covalent than the superoxides of other elements of this group. Taking into account the lowest electronegativity of all currently existing francium, it is characterized by pronounced chemical activity. All physical properties of this element are indicated only theoretically, since it is not possible to verify them in practice due to the short period of "life" of this element (density = 1.87 g / cm³, melting t = 27 ° C, boiling t = 677 ° C , specific heat of fusion=9.385 kJ/kg). All compounds of this element are soluble in water (exceptions: salts perchlorate, chloroplatinate, francium picratecobaltinitrite). Francium always co-crystallizes with substances containing cesium. Its co-precipitation with insoluble cesium salts (cesium perchlorate or cesium silicotungstate) is observed. Extraction from solutions of francium is carried out:
- cesium and rubidium chloroplatinates Cs 2 PtCl 6 and Rb 2 PtCl 6 ;
- chlorobismuth Cs 2 BiCl 5 , chlorostannate Cs 2 SnCl 6 and cesium chloroantimonate Cs 2 SbCl 5 2.5H 2 O;
- free heteropoly acids: silicotungstic and phosphotungstic.
What is the practical significance of this element?
Despite all its uniqueness, France has not yet been used in practice. Accordingly, it is not used in industry and any technologies. The reason for this is its extremely short half-life. There is evidence that francium chloride can be used to diagnose oncological neoplasms, however, due to the significant cost of this education, this kind of technique cannot be introduced into systematic use. In principle, cesium has the same properties.
Caesium
So this property of France turned out to be unclaimed: its cost is compared with the cost of a ton of platinum or gold. According to the forecasts of leading experts, the element in question will always have a purely cognitive value, nothing more.
