Strontium characteristics of the element according to plan. Atomic and molecular mass of strontium

Strontium metal is now produced by the aluminothermic method. SrO oxide is mixed with aluminum powder or shavings and at a temperature of 1100...1150°C in an electric vacuum oven (pressure 0.01 mm Hg) the reaction begins:

4SrO + 2Al → 3Sr + Al 2 O 3 SrO.

Electrolysis of strontium compounds (a method used by Davy) is less effective.

Applications of metal strontium

Strontium is an active metal. This prevents its widespread use in technology. But, on the other hand, the high chemical activity of strontium makes it possible to use it in certain areas of the national economy. In particular, it is used in the smelting of copper and bronze - strontium binds sulfur, phosphorus, carbon and increases the fluidity of slag. Thus, strontium helps purify the metal from numerous impurities. In addition, the addition of strontium increases the hardness of copper without almost reducing its electrical conductivity. Strontium is introduced into electric vacuum tubes to absorb remaining oxygen and nitrogen and make the vacuum deeper. Repeatedly purified strontium is used as a reducing agent in the production of uranium.

Additionally:

Strontium-90 (English strontium-90) - radioactive nuclide chemical element strontium With atomic number 38 andmass number 90. Formed mainly when nuclear fission V nuclear reactors And nuclear weapons.

To the environment 90 Sr enters mainly during nuclear explosions and emissions from NPP.

Strontium is an analogue calcium and is able to be firmly deposited in the bones. Long-term radiation exposure 90 Sr and its breakdown products affect bone tissue and bone marrow, which leads to the development radiation sickness, tumors of hematopoietic tissue and bones.

Application:

90 Sr is used in production radioisotope energy sources in the form of strontium titanate (density 4.8 g/cm³, energy release about 0.54 W/cm³).

One of the wide applications 90 Sr - control sources of dosimetric instruments, including military purposes and Civil Defense. The most common - type “B-8” is made as a metal substrate containing in a recess a drop of epoxy resin containing a compound 90 Sr. To provide protection against the formation of radioactive dust through erosion, the preparation is covered with a thin layer of foil. In fact, such sources of ionizing radiation are a complex 90 Sr- 90 Y, since yttrium is continuously formed during the decay of strontium. 90 Sr- 90 Y is an almost pure beta source. Unlike gamma radioactive drugs, beta drugs can be easily shielded with a relatively thin (about 1 mm) layer of steel, which led to the choice of beta drug for testing purposes, starting with the second generation of military dosimetric equipment (DP-2, DP-12, DP- 63).

Strontium is a silvery-white, soft, ductile metal. Chemically it is very active, like all alkaline earth metals. Oxidation state + 2. Strontium directly combines when heated with halogens, phosphorus, sulfur, carbon, hydrogen and even nitrogen (at temperatures above 400°C).

Conclusion

So, strontium is often used in chemistry, metallurgy, feather technology, nuclear power engineering, etc. And therefore, this chemical element is making its way into industry more and more confidently, and the demand for it is constantly growing. Strontium is also useful in medicine. The effect of natural strontium on the human body (low toxic, widely used for the treatment of osteoporosis). Radioactive strontium almost always has a negative effect on the human body.

Will nature be able to satisfy humanity’s needs for this metal?

In nature there are quite large so-called volcanogenic-sedimentary deposits of strontium, for example in the deserts of California and Arizona in the USA (By the way, it has been noted that strontium “loves” hot climates, so it is much less common in northern countries.). During the Tertiary era, this area was the scene of violent volcanic activity.

The thermal waters that rose along with lava from the bowels of the earth were rich in strontium. Lakes located among volcanoes accumulated this element, forming very substantial reserves over thousands of years.

There is strontium in the waters of Kara-Bogaz-Gol. The constant evaporation of the waters of the bay leads to the fact that the concentration of salts continuously increases and finally reaches the saturation point - the salts precipitate. The strontium content in these sediments is sometimes 1 - 2%.

Several years ago, geologists discovered a significant deposit of celestine in the mountains of Turkmenistan. Blue layers of this valuable mineral lie on the slopes of gorges and deep canyons of Kushtangtau, a mountain range in the southwestern part of the Pamir-Alai. There is no doubt that the Turkmen “heavenly” stone will successfully serve our national economy.

Nature is not characterized by haste: now man is using strontium reserves, which she began to create millions of years ago. But even today, in the depths of the earth, in the thickness of the seas and oceans, complex chemical processes occur, accumulations of valuable elements arise, new treasures are born, but they will no longer go to us, but to our distant, distant descendants.

Bibliography

Encyclopedia Around the World

http://www.krugosvet.ru/enc/nauka_i_tehnika/himiya/STRONTSI.html?page=0.3

Wikipedia "Strontium"

http://ru.wikipedia.org/wiki/%D0%A1%D1%82%D1%80%D0%BE%D0%BD%D1%86%D0%B8%D0%B9

3. Popular library of chemical elements

Strontium is an element of the main subgroup of the second group, the fifth period of the periodic system of chemical elements of D.I. Mendeleev, with atomic number 38. It is designated by the symbol Sr (lat. Strontium). The simple substance strontium (CAS number: 7440-24-6) is a soft, malleable and ductile alkaline earth metal, silver- white. It has high chemical activity; in air it quickly reacts with moisture and oxygen, becoming covered with a yellow oxide film.

History and origin of the name

The new element was discovered in the mineral strontianite, found in 1764 in a lead mine near the Scottish village of Stronshian, which later gave its name to the new element. The presence of a new metal oxide in this mineral was established in 1787 by William Cruickshank and Adair Crawford. Highlighted in pure form Sir Humphry Davy in 1808.

Receipt

There are 3 ways to obtain strontium metal:
1. thermal decomposition of some compounds
2. electrolysis
3. reduction of oxide or chloride
Main industrially The production of metal strontium is the thermal reduction of its oxide with aluminum. Next, the resulting strontium is purified by sublimation.
The electrolytic production of strontium by electrolysis of a melted mixture of SrCl 2 and NaCl is not widespread due to the low current efficiency and contamination of strontium with impurities.
The thermal decomposition of strontium hydride or nitride produces finely dispersed strontium, which is prone to easy ignition.

Chemical properties

Strontium in its compounds always exhibits a valence of +2. The properties of strontium are close to calcium and barium, occupying an intermediate position between them.
IN electrochemical series voltage, strontium is among the most active metals (its normal electrode potential is −2.89 V). Reacts vigorously with water to form hydroxide:
Sr + 2H 2 O = Sr(OH) 2 + H 2

Interacts with acids, displaces heavy metals from their salts. WITH concentrated acids(H 2 SO 4, HNO 3) reacts weakly.
Strontium metal quickly oxidizes in air, forming a yellowish film, in which, in addition to SrO oxide, SrO 2 peroxide and Sr 3 N 2 nitride are always present. When heated in air, it ignites; powdered strontium in air is prone to self-ignition.
Reacts vigorously with non-metals - sulfur, phosphorus, halogens. Interacts with hydrogen (above 200°C), nitrogen (above 400°C). Practically does not react with alkalis.
At high temperatures it reacts with CO 2, forming carbide:
5Sr + 2CO 2 = SrC 2 + 4SrO

Easily soluble strontium salts with the anions Cl - , I - , NO 3 - . Salts with anions F -, SO 4 2-, CO 3 2-, PO 4 3- are slightly soluble.

STRONTIUM (Strontium), Sr (a. strontium; n. Strontium; f. strontium; i. estroncio), — chemical element Group II periodic table Mendeleev, atomic number 38, atomic mass 87.62, refers to alkaline earth metals.

Properties of strontium

Natural strontium consists of 4 stable isotopes; 84 Sr (0.56%), 86 Sr (9.84%), 87 Sr (7.0%) and 88 Sr (82.6%); Over 20 artificial radioactive isotopes of strontium are known with mass numbers from 77 to 99, of which the most important has 90 Sr (TS 29 years), formed during the fission of uranium. Strontium was discovered in 1790 by the Scottish scientist A. Crawford in the form of an oxide.

In its free state, strontium is a soft golden-yellow metal. At t below 248°C it is characterized by a face-centered cubic lattice (a-Sr with a period a=0.60848 nm), in the range 248-577°C - hexagonal (b-Sr with periods a=0.432 nm, c=0.706 nm ); with more high temperature transforms into a body-centered cubic modification (g-Sr with a period a = 0.485 nm). Density of a-Sr 2540 kg/m 3 ; melting point 768°C, boiling point 1381°C; molar heat capacity 26.75 J/(mol.K); specific electrical resistance 20.0.10 -4 (Ohm.m), temperature coefficient linear expansion 20.6.10 -6 K -1. Strontium is paramagnetic, atomic magnetic susceptibility at room temperature is 91.2.10 -6. Plastic, soft, easy to cut with a knife.

Strontium by chemical properties similar to Ca and Ba. In compounds it has an oxidation state of +2. It oxidizes quickly in air, at room temperature it reacts with water, and at elevated temperatures with hydrogen, nitrogen, phosphorus, sulfur and halogens.

The average strontium content in the earth's crust is 3.4.10 -2% (by mass). Igneous medium rocks contain slightly more strontium (8.0.10 -2%) than (4.5.10 -2%), (4.4.10 -2%), (3.10 -2%) and (1.10 -3%) mountain rocks breeds About 30 strontium minerals are known, the most important of which are celestine SrSO 4 and strontianite SrCO 3 ; in addition, it is almost always present in calcium, potassium and barium minerals, entering them as an isomorphic impurity crystal lattice. Since of the 4 natural isotopes of strontium, one (87 Sr) constantly accumulates as a result of the R-decay of 87 Rb, the isotopic composition of strontium (87 Sr / 86 Sr ratio) is used in geochemical studies to establish genetic relationships between various rock complexes, as well as to determine their radiometric age (subject to simultaneous determination of rubidium content in the objects under study). Radioactive 90 Sr serves as pollution environment(until atmospheric cessation nuclear tests was one of the main factors of radioactive contamination).

Application and Use

The main raw materials for obtaining strontium are celestine and strontianite ores. Strontium metal is obtained by aluminothermic reduction of strontium oxide in vacuum. They are used in the manufacture of aluminum alloys and some steels, electric vacuum devices and some optical glasses. Strontium salts, which give the flame an intense red color, are used in pyrotechnics. 90 Sr is used in medicine as a source of ionizing radiation.

Long before the discovery of strontium, its undeciphered compounds were used in pyrotechnics to produce red lights. And until the mid-40s of the last century, strontium was primarily the metal of fireworks, fun and fireworks. Atomic Age made me look at him differently. Firstly, as a serious threat to all life on Earth; secondly, as material that can be very useful in solving serious problems in medicine and technology. But more on that later, let’s start with the history of “funny” metal, with a history in which the names of many great scientists are found.

Four times open "ground"

In 1764, a mineral was found in a lead mine near the Scottish village of Strontian, which was called strontianite. For a long time it was considered a type of fluorite CaF 2 or witherite BaCO 3 , but in 1790 the English mineralogists Crawford and Cruickshank analyzed this mineral and found that it contained a new “earth”, or, in today’s language, an oxide.

Independently of them, the same mineral was studied by another English chemist, Hop. Having come to the same results, he announced that strontianite contains a new element - metal strontium.

Apparently, the discovery was already “in the air”, because almost simultaneously the prominent German chemist Klaproth announced the discovery of a new “earth”.

In those same years, the famous Russian chemist, Academician Toviy Egorovich Lovitz, also came across traces of “strontian earth”. He had long been interested in the mineral known as heavy spar. In this mineral (its composition is BaSO 4), Karl Scheele discovered in 1774 the oxide of the new element barium. We don’t know why Lovitz was partial to heavy spar; we only know that the scientist who discovered the adsorption properties of coal and did much more in the field of general and organic chemistry, collected samples of this mineral. But Lovitz was not just a collector; he soon began to systematically study heavy spar and in 1792 came to the conclusion that this mineral contained an unknown impurity. He managed to extract quite a lot from his collection - more than 100 g of new “earth” and continued to explore its properties. The results of the study were published in 1795. Lowitz wrote then: “I was pleasantly surprised when I read ... the excellent article of Mr. Professor Klaproth on strontian earth, about which until then there was a very unclear idea. All the properties of hydrochloride and nitrate medium salts indicated by him in all points perfectly coincide with the properties of my same salts. I just had to check. The remarkable property of strontium earth is to color the alcohol flame in a carmine red color, and, indeed, my salt. fully possessed this property.”

So almost simultaneously several researchers in different countries came close to the discovery of strontium. But it was isolated in elemental form only in 1808.

The outstanding scientist of his time, Humphry Davy, already understood that the element strontium earth must apparently be an alkaline earth metal, and obtained it by electrolysis, i.e., in the same way as calcium, magnesium, and barium. To be more specific, then first in the world metal strontium was obtained by electrolysis of its moistened hydroxide. The strontium released at the cathode instantly combined with, forming an amalgam. By decomposing the amalgam by heating, Davy isolated the pure metal.

This metal is white, not heavy (density 2.6 g/cm3), quite soft, melting at 770°C. In terms of chemical properties, it is a typical representative of the alkaline earth metal family. The similarity with calcium, magnesium, and barium is so great that in monographs and textbooks the individual properties of strontium, as a rule, are not considered - they are analyzed using the example of calcium or magnesium.

And in the area practical applications These metals have more than once taken the way for strontium because they are more accessible and cheaper. This happened, for example, in sugar production. Once upon a time, a chemist discovered that using strontium disaccharate (C 12 H 22 O 4 * 2SrO), insoluble in water, it was possible to isolate sugar from molasses. Attention to strontium immediately increased, and more people began to receive it, especially in Germany and England. But soon another chemist found that a similar calcium saccharate was also insoluble. And interest in strontium immediately disappeared. It is more profitable to use cheap, more commonly found calcium.

This does not mean, of course, that strontium has completely “lost its face.” There are qualities that distinguish and set it apart from other alkaline earth metals. We will tell you about them in more detail.

Strontium metal red lights

This is what Academician A.E. Fersman called strontium. Indeed, as soon as you throw a pinch of one of the volatile strontium salts into the flame, the flame will immediately turn a bright carmine-red color. Strontium lines will appear in the flame spectrum.

Let's try to understand the essence of this simplest experience. There are 38 electrons in the five electron shells of the strontium atom. The three shells closest to the core are completely filled, and the last two have “vacancies.” In the burner flame, electrons are thermally excited and, acquiring more high energy, move from lower energy levels to upper ones. But such an excited state is unstable, and the electrons return to more favorable lower levels, releasing energy in the form of light quanta. A strontium atom (or ion) emits predominantly quanta with frequencies that correspond to the length of red and orange light waves. Hence the carmine-red color of the flame.

This property of volatile strontium salts has made them indispensable components of various pyrotechnic compositions. The red figures of fireworks, the red lights of signal and lighting flares are the “handiwork” of strontium.

Most often, nitrate Sr(NO 3) 2, oxalate SrC 2 O 4 and strontium carbonate SrCO 3 are used in pyrotechnics. Strontium nitrate is preferred: it not only colors the flame, but also serves as an oxidizer. When decomposing in a flame, it releases free oxygen:

Sr(NO 3) 2 → SrO + N2 + 2.502

Strontium oxide SrO colors the flame only pink. Therefore, chlorine is introduced into pyrotechnic compositions in one form or another (usually in the form of organochlorine compounds) so that its excess shifts the reaction equilibrium to the right:

2SrO + CI 2 → 2SrCl + O 2 .

The radiation of strontium monochloride SrCl is more intense and brighter than the radiation of SrO. In addition to these components, pyrotechnic compositions include organic and inorganic flammable substances, the purpose of which is to produce a large, uncolored flame.

There are quite a few recipes for red lights. Let us give two of them as an example. First: Sr(NO 3) 2 - 30%, Mg - 40%, resins - 5%,

hexachlorobenzene - 5%, potassium perchlorate KClO 4 - 20%. Second: potassium chlorate KClO 3 - 60%, SrC2O 4 - 25%, resin - 15%. Such compositions are not difficult to prepare, but it should be remembered that any, even the most proven, pyrotechnic compositions require “handling.” Homemade pyrotechnics are dangerous...

Strontium, glaze and enamel

The first glazes appeared almost at the dawn of pottery production. It is known that back in the 4th millennium BC. they were used to cover clay products. They noticed that if you cover pottery with a suspension of finely ground sand, potash and chalk in water, and then dry it and bake it in a kiln, the coarse clay powder will be covered with a thin film of a glassy substance and become smooth and shiny. The glassy coating closes the pores and makes the vessel impermeable to air and moisture. This glassy substance is the glaze. Later, clay products began to be coated first with paints and then with glaze. It turned out that the glaze prevents the paints from dulling and fading for quite a long time. Even later, glazes came into use in earthenware and porcelain production. Nowadays, ceramics and metal, porcelain and earthenware, and various construction products are covered with glaze.

What is the role of strontium here?

To answer this question, we will have to turn again to history. The basis of glazes is made up of various oxides. Alkaline (potash) and lead glazes have long been known. The former are based on silicon oxides, alkali metals(K and Na) and calcium. Secondly, lead oxide is also present. Later, glazes containing boron were widely used. Additions of lead and boron give glazes a mirror shine and better preserve underglaze paints. However, lead compounds are poisonous and boron is scarce.

In 1920, the American Hill first used a matte glaze, which included strontium oxides (Sr-Ca-Zn system). However, this fact went unnoticed, and only during the Second World War, when lead became especially scarce, did they remember Hill’s discovery. And an avalanche of research poured in: dozens (!) of strontium glaze recipes appeared in different countries. Attempts were also made to replace strontium with calcium, but calcium glazes turned out to be uncompetitive.

Strontium glazes are not only harmless, but also affordable (strontium carbonate SrCO 3 is 3.5 times cheaper than red lead). All the positive qualities of lead glazes are also characteristic of them. Moreover, products coated with such glazes acquire additional hardness, heat resistance, and chemical resistance.

Enamels - opaque glazes - are also prepared on the basis of silicon and strontium oxides. They are made opaque by the addition of titanium and zinc oxides. Porcelain items, especially vases, are often decorated with crackle glaze. Such a vase seems to be covered with a network of colored cracks. The basis of the “crackle” technology is different coefficients of thermal expansion of glaze and porcelain. Porcelain coated with glaze is fired at a temperature of 1280-1300°C, then the temperature is reduced to 150-220°C and the still not completely cooled product is dipped into a solution of coloring salts (for example, cobalt salts, if you need to get a black mesh). These salts fill the resulting cracks. After this, the product is dried and heated again to 800-850°C - the salts melt in the cracks and seal them. Crackle glaze is popular and widespread in many countries around the world. Works of decorative and applied art made in this manner are appreciated by amateurs. It remains to add that the use of strontium-free glazes provides a great economic effect.

Strontium radioactive

Another feature of strontium that sharply distinguishes it from the alkaline earth metals is the existence of the radioactive isotope strontium-90, which has been worrying biophysicists, physiologists, radiobiologists, biochemists and simply chemists for a long time.

As a result of a nuclear chain reaction, about 200 radioactive isotopes are formed from plutonium and uranium atoms. Most of them are short-lived. But the same processes also produce strontium-90 nuclei, whose half-life is 27.7 years. Strontium-90 is a pure beta emitter. This means that it emits streams of energetic electrons that act on all living things at relatively short distances, but very actively. Strontium, as an analogue of calcium, is actively involved in metabolism and, together with calcium, is deposited in bone tissue.

Strontium-90, as well as the daughter isotope yttrium-90 formed during its decay (with a half-life of 64 hours, emits beta particles) affect bone tissue and, most importantly, bone marrow, which is especially sensitive to radiation. Under the influence of irradiation, living matter undergoes chemical changes. The normal structure and functions of cells are disrupted. This leads to serious metabolic disorders in tissues. And as a result, the development of deadly diseases - blood cancer (leukemia) and bones. In addition, radiation acts on DNA molecules and, therefore, affects heredity. It has a detrimental effect.

The content of strontium-90 in the human body is directly dependent on the total power of the exploded atomic weapons. It enters the body by inhaling radioactive dust generated during the explosion and carried by the wind over long distances. Another source of infection is drinking water, plant and dairy foods. But in both cases, nature puts natural obstacles on the path of strontium-90 into the body. Only particles up to 5 microns in size can enter the finest structures of the respiratory organs, and few such particles are formed during an explosion. Secondly, during an explosion, strontium is released in the form of SrO oxide, the solubility of which in body fluids is very limited. The passage of strontium through the food system is prevented by a factor called “strontium-to-calcium discrimination.” It is expressed in the fact that with the simultaneous presence of calcium and strontium, the body prefers calcium. The Ca:Sr ratio in plants is twice that in soils. Further, the strontium content in milk and cheese is 5-10 times less than in grass used to feed livestock.

However, one cannot rely entirely on these favorable factors - they can only protect against strontium-90 to some extent. It is no coincidence that until testing of atomic and hydrogen weapons in three environments was banned, the number of victims from strontium grew from year to year. But the same terrible properties of strontium-90 - both powerful ionization and a long half-life - were turned to the benefit of humans.

Radioactive strontium has found application as an isotope tracer in studying the kinetics of various processes. It was by this method that in experiments with animals they established how strontium behaves in a living organism: where it is predominantly localized, how it participates in metabolism, and so on. The same isotope is used as a radiation source in radiation therapy. Applicators with strontium-90 are used in the treatment of eye and skin diseases. Strontium-90 preparations are also used in flaw detectors, in devices to combat static electricity, in some research instruments, and in nuclear batteries. There are no discoveries that are fundamentally harmful - the whole point is in whose hands the discovery ends up. The history of radioactive strontium is proof of this.

Strontium (Sr) - chemical element, alkaline earth metal of the 2nd group periodic table. Used in red signal lights and phosphors, it poses a major health hazard from radioactive contamination.

History of discovery

Mineral from a lead mine near the village of Strontian in Scotland. It was initially recognized as a type of barium carbonate, but Adair Crawford and William Cruikshank in 1789 suggested that it was a different substance. Chemist Thomas Charles Hope named the new mineral strontite after the village, and the corresponding strontium oxide SrO strontium. The metal was isolated in 1808 by Sir Humphry Davy, who electrolyzed a mixture of wet hydroxide or chloride and mercuric oxide using a mercury cathode, and then evaporated the mercury from the resulting amalgam. He named the new element using the root of the word “strontium”.

Being in nature

The relative abundance of strontium, the thirty-eighth element of the periodic table, in space is estimated to be 18.9 atoms for every 10 6 atoms of silicon. It makes up about 0.04% of the mass of the earth's crust. Average element concentration in sea ​​water equal to 8 mg/l.

The chemical element strontium occurs widely in nature and is estimated to be the 15th most abundant substance on Earth, reaching a concentration of 360 parts per million. Given its extreme reactivity, it exists only in the form of compounds. Its main minerals are celestine (SrSO 4 sulfate) and strontianite (SrCO 3 carbonate). Of these, celestite is found in quantities sufficient for profitable mining, more than 2/3 of the world supply of which comes from China, with Spain and Mexico supplying most remainder. However, it is more profitable to mine strontianite, because strontium is often used in carbonate form, but there are relatively few known deposits of it.

Properties

Strontium is a soft metal similar to lead that shines like silver when cut. In air, it quickly reacts with oxygen and moisture present in the atmosphere, acquiring a yellowish tint. Therefore, it must be stored in isolation from air masses. Most often it is stored in kerosene. It is not found in a free state in nature. Accompanying calcium, strontium is part of only 2 main ores: celestine (SrSO 4) and strontianite (SrCO 3).

In the series of chemical elements magnesium-calcium-strontium (alkaline earth metals), Sr is in group 2 (formerly 2A) of the periodic table between Ca and Ba. In addition, it is located in the 5th period between rubidium and yttrium. Since the atomic radius of strontium is similar to that of calcium, it easily replaces the latter in minerals. But it is softer and more reactive in water. Upon contact with it, it forms hydroxide and hydrogen gas. There are 3 known allotropes of strontium with transition points of 235°C and 540°C.

An alkaline earth metal generally does not react with nitrogen below 380°C and forms only an oxide at room temperature. However, in powder form, strontium spontaneously ignites to form oxide and nitride.

Chemical and physical properties

Characteristics of the chemical element strontium according to plan:

• Name, symbol, atomic number: strontium, Sr, 38.
• Group, period, block: 2, 5, s.
• Atomic mass: 87.62 g/mol.
• Electronic configuration: 5s 2 .
• Distribution of electrons across shells: 2, 8, 18, 8, 2.
• Density: 2.64 g/cm3.
• Melting and boiling points: 777 °C, 1382 °C.
• Oxidation state: 2.

Isotopes

Natural strontium is a mixture of 4 stable isotopes: 88 Sr (82.6%), 86 Sr (9.9%), 87 Sr (7.0%) and 84 Sr (0.56%). Of these, only 87 Sr is radiogenic - it is formed during the decay of the radioactive isotope of rubidium 87 Rb with a half-life of 4.88 × 10 10 years. It is believed that 87 Sr was produced during "primary nucleosynthesis" ( early stage Big Bang) along with the isotopes 84 Sr, 86 Sr and 88 Sr. Depending on the location, the ratio of 87 Sr and 86 Sr can differ by more than 5 times. It is used in dating geological samples and in determining the provenance of skeletons and clay artifacts.

As a result nuclear reactions About 16 synthetic radioactive isotopes of strontium were obtained, of which the most durable is 90 Sr (half-life 28.9 years). This isotope, formed when nuclear explosion, is considered the most dangerous product decay. Because of its chemical similarity to calcium, it is absorbed into bones and teeth, where it continues to push out electrons, causing radiation damage, damaging bone marrow, disrupting the formation of new blood cells, and causing cancer.

However, under medically controlled conditions, strontium is used to treat some superficial malignant neoplasms and bone cancer. It is also used in the form of strontium fluoride in radioisotope thermoelectric generators, in which its heat radioactive decay converted into electricity, serving as long-lived, lightweight energy sources in navigation buoys, remote weather stations and spacecraft.

89 Sr is used to treat cancer because it attacks bone tissue, produces beta irradiation, and decays after a few months (half-life 51 days).

The chemical element strontium is not necessary for higher forms life, its salts are usually non-toxic. What makes 90 Sr dangerous is that it is used to increase bone density and growth.

Connections

The properties of the chemical element strontium are very similar to In compounds, Sr has an exceptional +2 oxidation state in the form of the Sr 2+ ion. The metal is an active reducing agent and readily reacts with halogens, oxygen and sulfur to produce halides, oxides and sulfides.

Strontium compounds have fairly limited commercial value, since the corresponding calcium and barium compounds generally do the same thing but are cheaper. However, some of them have found application in industry. We have not yet figured out what substances can be used to achieve the crimson color in fireworks and signal lights. Currently, only strontium salts are used to obtain this color, such as Sr(NO 3) 2 nitrate and Sr(ClO 3) 2 chlorate. About 5-10% of the total production of this chemical element is consumed by pyrotechnics. Strontium hydroxide Sr(OH)2 is sometimes used to extract sugar from molasses because it forms a soluble saccharide from which sugar can be easily regenerated by the action of carbon dioxide. SrS monosulfide is used as a depilatory agent and an ingredient in the phosphors of electroluminescent devices and luminous paints.

Strontium ferrites form a family of compounds with general formula SrFe x Oy, obtained as a result of the high-temperature (1000-1300 °C) reaction of SrCO 3 and Fe 2 O 3. Ceramic magnets are made from them, which are found wide application in speakers, car windshield wiper motors and children's toys.

Production

Most mineralized celestine SrSO 4 is converted to carbonate in two ways: either the celestine is directly leached with sodium carbonate solution or it is heated with coal to form the sulfide. At the second stage, a dark-colored substance is obtained, containing mainly strontium sulfide. This “black ash” is dissolved in water and filtered. Strontium carbonate is precipitated from sulfide solution by introducing carbon dioxide. Sulfate is reduced to sulfide by carbothermic reduction SrSO 4 + 2C → SrS + 2CO 2 . The element can be produced by the cathodic electrochemical contact method, in which a cooled iron rod, acting as a cathode, touches the surface of a mixture of potassium and strontium chlorides, and is raised when the strontium solidifies on it. The reactions at the electrodes can be represented as follows: Sr 2+ + 2e - → Sr (cathode); 2Cl - → Cl 2 + 2e - (anode).

Sr metal can also be reduced from its oxide by aluminum. It is malleable and ductile, a good conductor of electricity, but is used relatively little. One of its uses is as an alloying agent for aluminum or magnesium in the casting of engine blocks. Strontium improves the machinability and creep resistance of the metal. An alternative way to obtain strontium is to reduce its oxide with aluminum in a vacuum at distillation temperature.

Commercial Application

The chemical element strontium is widely used in glass. cathode ray tubes color TVs to prevent X-ray penetration. It can also be included in aerosol paints. This appears to be one of the most likely sources of population exposure to strontium. In addition, the element is used to produce ferrite magnets and purify zinc.

Strontium salts are used in pyrotechnics because they color the flame red when burned. An alloy of strontium and magnesium salts is used in incendiary and signal mixtures.

Titanate has an extremely high refractive index and optical dispersion, making it useful in optics. It can be used as a substitute for diamonds, but is rarely used for this purpose due to its extreme softness and vulnerability to scratches.

Strontium aluminate is a bright phosphor with long-lasting phosphorescence. The oxide is sometimes used to improve the quality of ceramic glazes. The 90 Sr isotope is one of the best long-lived high-energy beta emitters. It is used as a power source for radioisotope thermoelectric generators (RTGs), which convert the heat released during decay into electricity. radioactive elements. These devices are used in spacecraft, remote weather stations, navigation buoys, etc. - where a lightweight and long-lived nuclear-electric energy source is required.

Medical uses of strontium: drug treatment

The isotope 89 Sr is the active ingredient radioactive drug Metastron, used to treat bone pain caused by metastatic prostate cancer. The chemical element strontium acts like calcium and is preferentially incorporated into bone in areas of increased osteogenesis. This localization focuses radiation exposure on the cancerous lesion.

The radioisotope 90 Sr is also used in cancer therapy. Its beta radiation and long-lasting radiation are ideal for superficial radiation therapy.

An experimental drug made by combining strontium with ranelinic acid promotes bone growth, increases bone density and reduces fractures. Stronium ranelate is registered in Europe as a treatment for osteoporosis.

Strontium chloride is sometimes used in toothpastes for sensitive teeth. Its content reaches 10%.

Precautionary measures

Pure strontium has high chemical activity, and when crushed, the metal spontaneously ignites. Therefore, this chemical element is considered a fire hazard.

Impact on the human body

The human body absorbs strontium in the same way as calcium. The two elements are chemically so similar that stable forms of Sr do not pose a significant health risk. In contrast, the radioactive isotope 90 Sr can lead to various bone disorders and diseases, including bone cancer. The strontium unit is used to measure the radiation of absorbed 90 Sr.