France metal color. Chemical element francium: structural features and chemical properties. An excerpt characterizing France

Elements of Mendeleev. By 1925, it was one of four missing elements. It is the heaviest and most active that exists in nature, and it is also the fastest for the half-life of existing chemical elements. This, and also the low nuclear stability, made it impossible for a long time to discover francium, the existence of which was predicted by Mendeleev almost a century before it was obtained.

The history of the discovery of the chemical element francium

It is distinctive in that it fell to the fate of a woman whose name is Marguerite Pere. The search for this substance was based on Based on the substances adjacent to No. 87, various hypotheses were put forward about the properties of this metal:

• due to the fact that the neighboring cesium melts at room temperature, it was assumed that the 87th element would also melt at low temperatures;
• it was thought to refer to such liquid metals as cesium or mercury;
• hypotheses about its radioactivity were put forward.

By the end of 1938, Marguerite Pere joined the search for this substance. She focused her attention on the alpha particles emitted by actinium. She well purified this substance from various impurities, leaving only a pure element. After lengthy chemical treatments, the alkaline salts remained in the hands of the scientist. She assumed that it was not radioactive, but after evaporation, beta activity became clearly visible with a half-life of 22 minutes. It immediately became clear to the woman that such a speed depends directly on the action of the alkaline element.

The long work of Margarita was crowned with success only in the autumn of 1939. Based on the existing nomenclature, the woman gave the 87th element the name "Actinium-K", which she later renamed francium in memory of the place where she was born. international union of theoretical and applied chemistry adopted the name coined by Margarita Pere. This is how France was discovered.

Chemical element Fr: characteristic

It is the heaviest and most reactive alkali metal found in nature, and it is also one of the fastest half-lives of the chemical elements in existence. The longest-lived of its isotopes can be found in uranium minerals. Therefore, the chemical element francium is very poorly understood, as it decays quickly. Moreover, it has a very high radioactivity. But still, small amounts of this element were investigated, and the following properties were discovered:

This is the last chemical element discovered in nature. It is one of the rarest, as it is very unstable and quickly decays. According to scientists, the chemical element francium is present on Earth in the amount of only 30 grams. It can be attributed to liquid metals, but it is liquid for a short time. After a few seconds, francium breaks down into more stable elements, in particular, radium is obtained.

France application

But, despite the high instability, this chemical element also benefits. It is used, although not widely. First of all, the chemical element francium is useful for detection in natural objects anemone. In addition, thanks to experiments with laboratory rats, scientists have found that it accumulates in malignant tumors that are in the first stage of development. Therefore, it can be used for early diagnosis of sarcoma. But research on this element continues. Francius reveals more and more of his secrets to scientists.

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 new element France (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. stable nuclide 223Fr (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 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.

The 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.

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 provide a more covalent bond between francium and oxygen in superoxides (for example, FrO 2 composition) relative to 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 test them in practice due to the short period of "life" of this element (density \u003d 1.87 g / cm³, melting t \u003d 27 ° C, boiling t \u003d 677 ° C, specific heat melting point=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.

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.

DEFINITION

France located in the seventh period of the I group of the main (A) subgroup of the Periodic Table.

Relates to elements s-families. Metal. Designation - Fr. Ordinal number - 87. Relative atomic mass - 223.02 a.m.u.

Electronic structure of the France atom

The francium atom consists of a positively charged nucleus (+87), inside which there are 87 protons and 136 neutrons, and 87 electrons move around in seven orbits.

Fig.1. Schematic structure of the francium atom.

The distribution of electrons in orbitals is as follows:

87Fr) 2) 8) 18) 32) 32) 8) 1 ;

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4f 14 5s 2 5p 6 5d 10 6s 2 6p 6 7s 1 .

The outer electronic level of the francium atom has 1 electron, which is a valence electron (located on the 7s sublevel). The energy diagram of the ground state takes the following form:

The presence of one unpaired electron in the francium atom indicates its ability to exhibit an oxidation state of +1.

The valence electron of a francium atom can be characterized by a set of four quantum numbers: n(chief quantum), l(orbital), m l(magnetic) and s(spin):

Examples of problem solving

EXAMPLE 1