Strontium chemical element. Strontium and its characteristics

Its name comes from the village of Strontian in Scotland, where the mineral containing strontium was discovered. In 1790, strontium was identified as an individual element by A. Crawford and W. Cruikshank. G. Davy first isolated metallic strontium in 1808.

Receipt:

Strontium accounts for 0.008% total number atoms of the earth's crust. In addition to silicate rocks, strontium occurs in the form of its sparingly soluble carbonic and sulphate salts: SrCO 3 - strontianite, SrSO 4 - celestine.
In the free state, it can be obtained by heating the oxide with metallic aluminum in high vacuum:
3SrO+2Al=Al 2 O 3 +3Sr

Physical properties:

Like calcium, strontium is a malleable golden yellow metal and is much softer than calcium. Volatile compounds of strontium color the flame carmine red.

Chemical properties:

In air, strontium is covered with a film containing, along with oxide, peroxide and strontium nitride. Due to rapid oxidation, the metal is stored in mineral oil or sealed in ampoules.
Reacts when heated with hydrogen and nitrogen, halogens. Easily displaces hydrogen not only from dilute acids, but also from water. Soluble in liquid ammonia. It is divalent in its compounds.

The most important connections:

Strontium oxide is a white refractory substance that vigorously attaches water to form a white hydroxide. Along with the oxide, white strontium(II) peroxide is known
Strontium hydroxide, Sr(OH) 2- strong base, highly soluble in water. When interacting with acids, the oxide and hydroxide easily form salts, usually colorless.
Strontium nitrate, Sr(NO 3) 2 is allocated in the form of crystalline hydrates, which are very easily soluble in water. Nitrates are similar in composition to chlorates, bromates, and iodates.
The solubility of salts in water decreases in the series: Ca - Sr - Ba and Cl - Br - I.
Strontium sulfide is a white solid. Strontium polysulfides SrS n are known.

Application:

Strontium is a getter in electrovacuum devices, a modifier of alloys, cast irons and steels. Radioactive isotopes 89 Sr and 90 Sr are used as sources b-radiation.
Strontium nitrate is used in pyrotechnics for the manufacture of compositions that, when burned, give a brightly colored red flame (fireworks and flares).
Many strontium compounds are used as components of ceramics, phosphors, and optical materials.
Strontium is able to accumulate in the human body, replacing calcium, which leads to increased bone fragility. But if it is not natural strontium, but 90 Sr formed as a result of nuclear explosions, then the consequences are much more severe: bone marrow damage, leukemia, radiation sickness.

Elmik Galina

See also:
S.I. Venetsky. About the rare and scattered. Metal stories.

STRONTIUM (Strontium, Sr) - chemical element periodic system of D. I. Mendeleev, subgroups of alkaline earth metals. In the human body, S. competes with calcium (see) for inclusion in the crystal lattice of bone oxyapatite (see). 90 Sr, one of the most long-lived radioactive fission products of uranium (see), accumulating in the atmosphere and biosphere during nuclear weapons tests (see), poses a great danger to mankind. S.'s radioactive isotopes are used in medicine for radiation therapy (see), as a radioactive label in diagnostic radiopharmaceuticals (see) in medical biol. research, as well as in atomic electric batteries. S. compounds are used in flaw detectors, in sensitive instruments, and in devices for combating static electricity. In addition, S. is used in radio electronics, pyrotechnics, in the metallurgical and chemical industries, and in the manufacture of ceramic products. S.'s connections are not poisonous. When working with metallic S., one should be guided by the rules for handling alkali metals (see) and alkaline earth metals (see).

S. was discovered as part of a mineral later named SrC03 strontianite in 1787 near the Scottish city of Strontiana.

The serial number of strontium is 38, the atomic weight (mass) is 87.62. The content of S. in the earth's crust averages 4-10 2 wt. %, in sea ​​water- 0.013% (13 mg/l). The minerals strontianite and celestite SrSO 4 are of industrial importance.

The human body contains approx. 0.32 g of strontium, mainly in bone tissue, in the blood, the concentration of S. is normally 0.035 mg / l, in the urine - 0.039 mg / l.

S. is a soft silvery-white metal, t°pl 770°, t°kip 1383°.

According to chem. S.'s properties are similar to calcium and barium (see), in compounds the valence of strontium is 4-2, it is chemically active, it is oxidized at normal conditions water with the formation of Sr (OH) 2, as well as oxygen and other oxidizing agents.

S. enters the human body hl. arr. with plant foods, as well as with milk. It is absorbed in the small intestine and quickly exchanges with S. contained in the bones. S.'s removal from an organism is strengthened by complexes, amino acids, polyphosphates. The increased content of calcium and fluorine (see) in water interferes with S.'s cumulation in bones. With an increase in the concentration of calcium in the diet by 5 times, S.'s accumulation in the body is halved. Excessive intake of S. with food and water due to its high content in the soil of some geochem. provinces (eg, in some districts of Eastern Siberia) causes an endemic disease - ur disease (see Kashin - Beck disease).

In bones, blood and other biol. S.'s substrates define hl. arr. spectral methods (see Spectroscopy).

radioactive strontium

Natural S. consists of four stable isotopes with mass numbers 84, 86, 87, and 88, of which the latter is the most common (82.56%). Eighteen radioactive isotopes of sulfur are known (with mass numbers 78–83, 85, 89–99) and four isomers of isotopes with mass numbers 79, 83, 85, and 87 (see Isomerism).

In medicine, 90Sr is used for radiation therapy in ophthalmology and dermatology, as well as in radiobiological experiments as a source of β-radiation. 85Sr is produced either by irradiating a strontium target enriched in the 84Sr isotope with neutrons in a nuclear reactor by the reaction 84Sr (11.7) 85Sr, or produced at a cyclotron by irradiating natural rubidium targets with protons or deuterons, for example, by the reaction 85Rb (p, n) 85Sr. The radionuclide 85Sr decays with electron capture, emitting gamma radiation with an energy E gamma equal to 0.513 MeV (99.28%) and 0.868 MeV (< 0,1%).

87mSr can also be obtained by irradiating a strontium target in a reactor by the reaction 86Sr (n, gamma) 87mSr, but the yield of the desired isotope is low, in addition, 85Sr and 89Sr isotopes are formed simultaneously with 87mSr. Therefore, usually 87niSr is obtained using an isotope generator (see Radioactive Isotope Generators) based on the parent isotope of yttrium-87 - 87Y (T1 / 2 = 3.3 days). 87mSr decays with an isomeric transition, emitting gamma radiation with an Egamma energy of 0.388 MeV, and partly with electron capture (0.6%).

89Sr is contained in fission products together with 90Sr; therefore, 89Sr is obtained by irradiating natural sulfur in a reactor. In this case, an 85Sr impurity is also inevitably formed. The 89Sr isotope decays with the emission of P-radiation with an energy of 1.463 MeV (approx. 100%). The spectrum also contains a very weak line of gamma radiation with an energy E gamma equal to 0.95 MeV (0.01%).

90Sr is obtained by isolation from a mixture of uranium fission products (see). This isotope decays with the emission of beta radiation with an energy of E beta equal to 0.546 Meu (100%), without accompanying gamma radiation. The decay of 90Sr leads to the formation of a daughter radionuclide 90Y, which decays (T1 / 2 = 64 hours) with the emission of p-radiation, consisting of two components with Ep equal to 2.27 MeV (99%) and 0.513 MeV (0 .02%). The decay of 90Y also emits very weak gamma radiation with an energy of 1.75 MeV (0.02%).

Radioactive isotopes 89Sr and 90Sr, which are present in the waste of the nuclear industry and are formed during nuclear weapons testing, can enter the human body with food, water, and air when the environment is polluted. Quantification of S.'s migration in the biosphere is usually carried out in comparison with calcium. In most cases, when 90Sr moves from the previous link in the chain to the next, the concentration of 90Sr decreases per 1 g of calcium (the so-called discrimination coefficient), in adults in the body-diet link, this coefficient is 0.25.

Like soluble compounds of other alkaline earth elements, soluble compounds of S. are well absorbed from went. - kish. a path (10-60%), absorption of poorly soluble connections S. (eg, SrTi03) makes less than 1%. The degree of absorption of S.'s radionuclides in the intestine depends on age. With an increase in the calcium content in the diet, S.'s accumulation in the body decreases. Milk promotes increase in S.'s absorption and calcium in intestines. It is believed that this is due to the presence of lactose and lysine in milk.

When inhaled, soluble S. compounds are quickly eliminated from the lungs, while poorly soluble SrTi03 is exchanged in the lungs extremely slowly. Penetration of radionuclide S. through the intact skin makes apprx. one%. Through damaged skin (cut wound, burns, etc.)? as well as from subcutaneous tissue and muscle tissue, S. is absorbed almost completely.

S. is an osteotropic element. Regardless of the route and rhythm of entry into the body, soluble 90Sr compounds selectively accumulate in the bones. Less than 1% of 90Sr is retained in soft tissues.

With intravenous administration, S. is very quickly eliminated from the bloodstream. Soon after administration, the concentration of S. in the bones becomes 100 times or more higher than in soft tissues. Nek-ry distinctions in accumulation 90Sr in separate bodies and fabrics are noted. A relatively higher concentration of 90Sr in experimental animals is found in the kidneys, salivary and thyroid glands, and the lowest concentration is found in the skin, bone marrow and adrenal glands. The concentration of 90Sr in the renal cortex is always higher than in the medulla. S. initially lingers on the bone surfaces (periosteum, endosteum), and then is distributed relatively evenly throughout the entire volume of the bone. However, the distribution of 90Sr in various parts the same bone and in different bones is uneven. During the first time after injection, the concentration of 90Sr in the epiphysis and metaphysis of the bone of experimental animals is approximately 2 times higher than in the diaphysis. From the epiphysis and metaphysis, 90Sr is excreted faster than from the diaphysis: in 2 months. the concentration of 90Sr in the epiphysis and metaphysis of the bone decreases by 4 times, and in the diaphysis almost does not change. Initially 90Sr concentrates in those sites in which there is an active formation of a bone. Abundant blood and lymph circulation in the epimetaphyseal areas of the bone contributes to a more intense deposition of 90Sr in them compared to the diaphysis of the tubular bone. The amount of 90Sr deposition in the bones of animals is not constant. A sharp decrease in 90Sr fixation in bones with age was found in all animal species. Deposition of 90Sr in the skeleton significantly depends on gender, pregnancy, lactation, and the state of the neuroendocrine system. A higher deposition of 90Sr in the skeleton was noted in male rats. In the skeleton of pregnant females, 90Sr accumulates less (up to 25%) than in control animals. Lactation has a significant effect on the accumulation of 90Sr in the skeleton of females. With the introduction of 90Sr 24 hours after birth, 90Sr is retained in the skeleton of rats 1.5-2 times less than in non-lactating females.

The penetration of 90Sr into the tissues of the embryo and fetus depends on the stage of their development, the state of the placenta, and the duration of circulation of the isotope in the mother's blood. Penetration of 90Sr into the fetus is the greater longer term pregnancy at the time of radionuclide administration.

To reduce the damaging effect of strontium radionuclides, it is necessary to limit their accumulation in the body. For this purpose, when the skin is contaminated, it is necessary to quickly decontaminate its open areas (Protection-7 preparation, Era or Astra washing powders, NEDE paste). In case of oral intake of strontium radionuclides, antidotes should be used to bind or absorb the radionuclide. Such antidotes include activated barium sulfate (adso-bar), polysurmin, alginic acid preparations, etc. For example, the drug adsobar, when taken immediately after radionuclides enter the stomach, reduces their absorption by 10-30 times. Adsorbents and antidotes should be prescribed immediately after detection of damage by strontium radionuclides, since delay in this case leads to a sharp decrease in their positive effect. At the same time, it is recommended to prescribe emetics (apomorphine) or to produce abundant gastric lavage, use saline laxatives, cleansing enemas. In case of damage by dust-like preparations, abundant washing of the nose and oral cavity, expectorants (thermopsis with soda), ammonium chloride, injections of calcium preparations, diuretics are necessary. In more late dates after the defeat, to reduce the deposition of radionuclides S. in the bones, it is recommended to use the so-called. stable strontium (S. lactate or S. gluconate). Large doses of oral calcium or intravenous MofyT replace stable strontium preparations if these are not available. In connection with the good reabsorption of strontium radionuclides in the renal tubules, the use of diuretics is also indicated.

Nek-swarm decrease in accumulation of S.'s radionuclides in an organism can be reached by creation of competitive relations between them and stable isotope S. or calcium, and also creation of deficiency of these elements when S.'s radionuclide was already fixed in a skeleton. However effective means decorporation of radioactive strontium from the body has not yet been found.

The minimum significant activity that does not require registration or permission from the State Sanitary Inspection for 85mSr, 85Sr, 89Sr and 90Sr is 3.5*10 -8 , 10 -10 , 2.8*10 -11 and 1.2*10, respectively -12 curies/l.

Bibliography: Borisov V.P. and others. Emergency care for acute radiation exposure, M., 1976; Buldakov L. A. and Moskalev Yu. I. Problems of distribution and experimental estimation acceptable levels Cs137, Sr90 and Ru106, M., 1968, bibliogr.; Voinar A.I. Biological role microelements in the organism of animals and humans, p. 46, M., 1960; Ilyin JI. A. and Ivannikov A. T. Radioactive substances and wounds, M., 1979; To and with and in fi-on B. S. and T about r ben to about V. P. Life of a bone tissue, M., 1979; JI e in and V. I N. Obtaining radioactive preparations, M., 1972; Metabolism of strontium, ed. J. M. A. Lenihena and others, trans. from English, M., 1971; Poluektov N. S. and others. Analytical chemistry of strontium, M., 1978; P em and G. Course of inorganic chemistry, trans. from German, vol. 1, M., 1972; Protection of the patient in radionuclide investigations, Oxford, 1969, bibliogr.; Table of isotopes, ed. by C. M. Lederer a. V. S. Shirley, N. Y. a. o., 1978.

A. V. Babkov, Yu. I. Moskalev (rad.).

Strontium

STRONTIUM-I; m.[lat. strontium] A chemical element (Sr), a light, silvery-white metal whose radioactive isotopes are used in nuclear testing and engineering.

◁ Strontium, th, th.

(lat. Strontium), a chemical element of group II of the periodic system, belongs to the alkaline earth metals. Named after the mineral strontianite found near the village of Strontian in Scotland. Silver white metal; density 2.63 g / cm 3, t pl 768°C. It is chemically very active, so the metal itself is used little (in the smelting of copper and bronze for their purification, in electrovacuum technology as a getter), salt is used in the production of paints, luminous compositions, glazes and enamels. SrTiO 3 is a ferroelectric. During nuclear explosions, a radioactive isotope 90 Sr (half-life 29.1 years) is formed in nuclear reactors, which poses a great danger to humans when it enters the natural environment.

STRONTIUM (lat. Strontium, from the village of Srtrontian in Scotland, near which it was found), a chemical element with atomic number 38, atomic mass 87.62. The chemical symbol is Sr, which reads "strontium". It is located in the 5th period in group IIA of the periodic system of elements. alkaline earth metal. Natural strontium consists of four stable isotopes with mass numbers 84 (0.56% by mass), 86 (9.86%), 87 (7.02%), and 88 (82.56%).
Outer electron layer configuration 5 s 2 . The oxidation state is +2 (valency II). The radius of the atom is 0.215 nm, the radius of the Sr 2+ ion is 0.132 nm (coordination number 6). Sequential ionization energies are 5.6941 and 11.0302 eV. Electronegativity according to Pauling (cm. PAULING Linus) 1,0.
Strontium is a soft silvery white relatively light metal.
Discovery history
In 1764 a new mineral, strontianite, was discovered in a lead mine. In 1890, the Englishman A. Crawford and, at the same time, the Englishman T. Hope, the German chemist M. Klaproth (cm. KLAPROT Martin Heinrich) and Russian academician T. E. Lovitz (cm. LOVITS Tovy Egorovich) the oxide of a new element was isolated from strontianite. In 1808, the English chemist G. Davy obtained an amalgam of strontium. (cm. DEVI Humphrey).
Prevalence in nature
The content in the earth's crust is 0.034% by weight. It does not occur in free form. The most important minerals: strontianite (cm. strontianite) and celestine (cm. CELESTIN) SrSO4. As an impurity, it is contained in calcium minerals, for example, in fluorapatite 3Ca 3 (PO 4) 2 CaF 2.
Receipt
The main source of raw materials in the production of strontium and its compounds - celestine SrSO 4 - is first reduced with coal under strong heating:
SrSO 4 + 4C \u003d SrS + 4CO
Then strontium sulfide SrS with hydrochloric acid (cm. HYDROCHLORIC ACID) converted to SrCl 2 and dehydrated. To obtain Sr, its chloride is reduced with magnesium. (cm. MAGNESIUM) in a hydrogen atmosphere:
SrCl 2 + Mg = MgCl 2 + Sr
Strontium is also obtained by reduction of SrO with aluminum (cm. ALUMINUM), silicon (cm. SILICON) or ferrosilicon:
4SrO + 2Al = 3Sr + SrAl 2 O 4
Physical and chemical properties
Strontium is a soft, silvery-white metal that comes in three forms. Up to 231°C, the a-modification with a cubic face-centered lattice of the Cu type is stable, a= 0.6085 nm. At 231-623°C - b-modification with a hexagonal lattice, at 623°C up to the melting point (768°C) - g-modification with a cubic body-centered lattice. Boiling point 1390°C, density 2.63 kg/dm 3 . Strontium is a malleable, ductile metal.
Strontium is chemically highly active. Standard electrode potential Sr 2+ /Sr - 2.89 V.
At room temperature in air, strontium is covered with a film of SrO oxide and SrO 2 peroxide. It ignites when heated in air. interacting with halogens, (cm. HALOGENS) forms halides SrCl 2 and SrBr 2 . When heated to 300-400°C, it reacts with hydrogen (cm. HYDROGEN), forming a hydride SrH 2 . By heating strontium in an atmosphere of CO 2, one obtains:
5Sr + 2CO 2 = SrC 2 + 4SrO
Strontium actively reacts with water:
Sr + 2H 2 O \u003d Sr (OH) 2 + H 2
When heated, strontium interacts with nitrogen, sulfur, selenium and other non-metals to form Sr 3 N 2 nitride, SrS sulfide, SrSe selenide, and so on.
Strontium oxide - basic, interacts with water, forming hydroxide:
SrO + H 2 O \u003d Sr (OH) 2
When interacting with acid oxides, SrO forms salts:
SrO + CO 2 \u003d SrCO 3
Sr 2+ ions are colorless. SrCl 2 chloride, SrBr 2 bromide, SrI 2 iodide, Sr(NO 3) 2 nitrate are highly soluble in water and color the flame carmine red. Insoluble carbonate SrCO 3 , sulfate SrSO 4 , average orthophosphate Sr 3 (PO 4) 2 .
Application
Strontium is used as an alloying addition to alloys based on magnesium, aluminum, lead, nickel and copper. Strontium is a part of getters. Strontium compounds are used in pyrotechnics, are part of luminescent materials, emission coatings of radio lamps, and are used in the manufacture of glasses.
Strontium titanate SrTiO 3 is used in the manufacture of dielectric antennas, piezoelectric elements, small-sized non-linear capacitors, as infrared radiation sensors. 90 Sr preparations are used in radiation therapy of skin and some eye diseases.
Physiological action
Strontium compounds are toxic. When ingested, damage to bone tissue and liver is possible. MPC of strontium in water 8 mg/l, in air for hydroxide, nitrate and oxide 1 mg/m 3 , for sulfate and phosphate 6 mg/m 3 .
Problems 90 Sr
In case of explosions of nuclear charges or due to the leakage of radioactive waste into environment the radioactive isotope 90 Sr enters. Forming highly water-soluble bicarbonate Sr(HCO 3) 2 , 90 Sr migrates into water, soil, plants and animal organisms.

encyclopedic Dictionary. 2009 .

See what "strontium" is in other dictionaries:

- (new lat.). light metal yellow color, named after the village in Scotland, in the vicinity of which it was discovered for the first time; in combination with carbon dioxide forms the mineral strontianite. Dictionary foreign words included in the Russian language. ... ... Dictionary of foreign words of the Russian language

Table of nuclides General information Name, symbol Strontium 90, 90Sr Alternative names Radio strontium Neutrons 52 Protons 38 Nuclide properties Atomic mass 8 ... Wikipedia

STRONTIUM- chem. element, symbol Sr (lat. Strontium), at. n. 38, at. m. 87.62; belongs to the alkaline earth metals, has a silvery White color, density 2630 kg/m3, tm = 768 °С. It is chemically very active, so little is used in its pure form. Use… Great Polytechnic Encyclopedia

Chem. element II gr. periodic system, serial number 38, at. in. 87, 63; consists of 4 stable isotopes. The average isotopic composition of ordinary S. is as follows: Sr84 0.56%, Si86 9.86%, Sr87 7.02%, Sr88 82.56%. One of the isotopes of C. Sr87 ... ... Geological Encyclopedia

Celestin Dictionary of Russian synonyms. strontium n., number of synonyms: 5 foreigner (23) metal ... Synonym dictionary

- (Strontium), Sr, chemical element of group II of the periodic system, atomic number 38, atomic mass 87.62; soft alkaline earth metal. As a result nuclear testing, accidents at nuclear power plants and with radioactive waste enters the environment ... ... Modern Encyclopedia

- (lat. Strontium) Sr, a chemical element of group II of the periodic system, atomic number 38, atomic mass 87.62, belongs to the alkaline earth metals. Named after the mineral strontianite, found near the village of Strontian in Scotland. ... ... Big Encyclopedic Dictionary- (Strontium), Sr, chem. element II group periodic. systems of elements, at. number 38, at. weight 87.62, alkaline earth metal. Natural S. is a mixture of stable 84Sr, 86Sr 88Sr, in which 88Sr (82.58%) predominates, and 84Sr (0.56%) is the least. ... ... Physical Encyclopedia

DEFINITION

Strontium is the thirty-eighth element of the Periodic Table. Designation - Sr from the Latin "strontium". Located in the fifth period, IIA group. Refers to metals. The core charge is 38.

Strontium occurs in nature mainly as sulfates and carbonates, forming the minerals celestite SrSO 4 and strontianite SrCO 3 . The content of strontium in the earth's crust is 0.04% (mass.).

Metallic strontium in the form of a simple substance is a soft silvery-white (Fig. 1) metal with malleability and plasticity (it is easily cut with a knife). Reactive: oxidizes rapidly in air, interacts quite vigorously with water, and combines directly with many elements.

Rice. 1. Strontium. Appearance.

Atomic and molecular weight of strontium

DEFINITION

Relative molecular weight of a substance (M r) is a number showing how many times the mass of a given molecule is greater than 1/12 of the mass of a carbon atom, and relative atomic mass of an element (A r)- how many times the average mass of atoms of a chemical element is greater than 1/12 of the mass of a carbon atom.

Since strontium exists in the free state in the form of monatomic Sr molecules, the values ​​of its atomic and molecular masses coincide. They are equal to 87.62.

Allotropy and allotropic modifications of strontium

Strontium exists in the form of three crystalline modifications, each of which is stable in a certain temperature range. So, up to 215 o C, α-strontium is stable (face-centered cubic lattice), above 605 o C - g - strontium (body-centered cubic lattice), and in the temperature range 215 - 605 o C - b-strontium (hexagonal lattice).

Isotopes of strontium

It is known that in nature rubidium can be in the form of the only stable isotope 90 Sr. The mass number is 90, the atomic nucleus contains thirty-eight protons and fifty-two neutrons. Radioactive.

Strontium ions

At the outer energy level of the strontium atom, there are two electrons that are valence:

1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 5s 2 .

As a result of chemical interaction, strontium gives up its valence electrons, i.e. is their donor, and turns into a positively charged ion:

Sr 0 -2e → Sr 2+ .

Molecule and atom of strontium

In the free state, strontium exists in the form of monatomic Sr molecules. Here are some properties that characterize the atom and molecule of strontium:

Strontium alloys

Strontium found wide application in metallurgy as an alloying component of copper-based alloys.

Examples of problem solving

EXAMPLE 1

General Information and Acquisition Methods

Strontium (Sr) is a silver-white metal. A mineral containing strontium was discovered in 1787 in Scotland in a lead mine near the village of Strontian and named strontianite. In 1790, the Scottish mineralogists Crawford and Cruikshank studied this mineral in detail and discovered a new "earth" (oxide) in it. Regardless of them, their compatriot chemist Hop found that this mineral contains a new element - strontium. The German chemist Klaproth came to the same conclusion. In the same years, the famous Russian chemist Acad. T. E. Lovitz discovered traces of strontium in heavy spar. The results of his research were published in 1795. However pure metal was allocated only in 1808 by Davy. In 1924, Danner (USA) obtained pure strontium by reducing it from oxide with metallic aluminum (or magnesium).

Strontium metal is currently produced mainly by the aluminothermic method. Strontium oxide is mixed with aluminum powder, briquetted and placed in an electric vacuum furnace (vacuum 1.333 Pa), where metal is reduced at 1100-1150 °C.

Strontium is produced in accordance with TsMTU 4764-56 of three grades (Ch, ChDA and HCh) in the form of rods and crystals (druze).

Salts and strontium compounds are toxic (cause paralysis, affect vision). When working with them, you should follow the safety regulations with salts of alkali and alkaline earth metals.

Physical properties

Atomic characteristics. Atomic number 38, atomic mass 87.62 amu. e. m, atomic volume 33.7 * 10 -6 m 3 / mol, atomic radius 0.215 nm, ionic radius 0.127 nm. Ionization potentials J (eV): 5.692; 11.026; 43.6. Electronegativity 1.0. Strontium has g. c. to the lattice (a - Sr) with a period a \u003d 0.6085 nm, the energy of the crystal lattice is 164.3 μJ / kmol, the coordination number is 12, the interatomic distance is 4.30 nm. At a temperature of 488 K, an a -6 transformation occurs. 6-strontium has a hexagonal lattice with periods a = 0.432 nm, c - = 0.706 nm, c / a = 1.64. At 605 °C, the 6->-y-polymorphic transformation takes place. The formative cubic bulk-caught modification has a period a=0.485 nm. Electronic configuration of the outer layer 5 s 2 . Natural strontium consists of four stable isotopes: 84 Sr (0.58%), 86 Sr (9.88%), 87 Sr (7.2%). 88Sr (82.58%). 14 artificial unstable isotopes have also been obtained. The radioactive isotope 90 Sr with a half-life of 27.7 years is formed in nuclear reactions (uranium fission). The effective cross-section of capture of thermal neutrons is 1.21*10 -28 m 2 . The work function of electrons φ=2.35 eV, for single crystal (100) φ=2.43 eV.

The density p at 273 K is 2.630 Mg/m 3 .

Magnetic susceptibility at a temperature of 293 K x = +1.05-10^ 9 .

Chemical properties

The normal electrode potential of the reaction Sr -2 e \u003d? * Sr 2 + cp 0 \u003d 2.89 V. +2 oxidation state.

Strontium is a very active element; it oxidizes rapidly in air, releasing a large number heat, vigorously decomposes water. It interacts with hydrogen elevated temperature 300-400°C, forming a hydride SrH 2 with a melting point of 650°C. With oxygen, it forms oxide (II) SrO with a melting point of 2430 ° C, at 500 ° C and a pressure of 15 MPa - oxide (IV) Sr 0 2. It interacts with nitrogen at 380-400 ° C and gives the Sr 3 N 2 compound.

When heated, strontium easily interacts with halogens, forming the corresponding salts: SrCl 2 chloride with a melting point of 872 ° C, SrBr 2 bromide with a melting point of 643 ° C, SrF 2 fluoride with a melting point of 1190 ° C, Srl 2 iodide. With carbon it forms strontium carbide SrC 2 , with phosphorus - strontium phosphide SrP 2 , with sulfur when heated - sulfides.

It interacts weakly with concentrated nitric and sulfuric acids, vigorously with dilute ones; with alkalis - NaOH, KOH (concentrated and diluted) also reacts.

Forms solid solutions with metals and metal compounds

niya In a liquid state, it mixes with elements of PA, PV - VB subgroups (Be, Mg, Zn, Cd, Hg, Al, Ga, In, TI, Sn, Pb, Sb, Bi, As). With many of them it forms metal connections(Al, Mg, Zn, Sn, Pb, etc.). With some transition and noble metals gives immiscible systems. Most metals of the platinum group are characterized by the formation of Laves-type phases with strontium. With elements of the P1V subgroup, it forms phases of the AB 4 type. Electrochemical equivalent 0.45404 mg/C.

Technological properties

Strontium is a malleable and ductile metal. Forging from it can be obtained thin sheet, and by pressing at 230 ° C - wire.

Areas of use

Metallic strontium and its compounds are used in industry. The introduction of this element and its compounds in steel and cast iron improves their quality. There is information about the use of strontium for the deoxidation and refining of copper; this also increases the hardness. The introduction of 0.1% Sr into titanium and its alloys increases the impact strength; strontium increases the plasticity of magnesium and its alloys, positively affects the properties of aluminum alloys.

Strontium compounds are used in pyrotechnics, in electrovacuum technology (gas absorber), in radio electronics (for the manufacture of photocells). Strontium is a component of oxide cathodes used in cathode-ray tubes, microwave lamps, etc.

In glassmaking, strontium is used to produce special optical glasses; it increases the chemical and thermal stability of the glass and the refractive indices. So, glass containing 9 °, "0 SrO, has high abrasion resistance and high elasticity, can be easily machined (twisted, processed into yarn and fabric). In our country, a technology has been developed for obtaining strontium-containing glass without boron. Such glass has a high chemical resistance, strength and electrical properties.The ability of strontium glasses to absorb X-rays from tubes of color TVs, as well as to improve radiation resistance.Strontium fluoride is used to produce lasers and optical ceramics.Strontium hydroxide is used in oil industry for the production of lubricating oils with increased resistance to oxidation, and in the food industry, for the processing of sugar production waste in order to additionally extract sugar. Strontium compounds are also part of enamels, glazes and ceramics. They are widely used in the chemical industry as rubber fillers, plastic stabilizers, as well as for the purification of caustic soda from iron and manganese, as catalysts in organic synthesis and in oil cracking, etc. .