Strontium is a chemical element with atomic number 38 [4] . It belongs to the 2nd group of the periodic table of chemical elements (according to the outdated short form of the periodic system it belongs to the main subgroup of group II, or to group IIA), it is in the fifth period of the table. Atomic mass of the element 87.62 (1) a. e. m. [1] . It is designated by the symbol Sr (from lat. Strontium ). The simple substance of strontium is a soft, malleable and ductile alkaline earth metal of silver-white color . It has high chemical activity, quickly reacts with moisture and oxygen in the air, becoming covered with a yellow oxide film .
| Strontium | ||||
|---|---|---|---|---|
| β Rubidium | Yttrium β | ||||
| ||||
| The appearance of a simple substance | ||||
| Soft silver white metal | ||||
 | ||||
| Atom properties | ||||
| Name, symbol, number | Strontium / Strontium (Sr), 38 | |||
| Atomic mass ( molar mass ) | 87.62 (1) [1] a. E. m. ( g / mol ) | |||
| Electronic configuration | [Kr] 5s 2 | |||
| Atom radius | 215 pm | |||
| Chemical properties | ||||
| Covalent radius | 191 pm | |||
| Ion radius | (+ 2e) 112 pm | |||
| Electronegativity | 0.95 (Pauling scale) | |||
| Electrode potential | β2.89 | |||
| Oxidation state | 2 | |||
| Ionization energy (first electron) | 549.0 (5.69) kJ / mol ( eV ) | |||
| Thermodynamic properties of a simple substance | ||||
| Density (at N. at. ) | 2.54 g / cmΒ³ | |||
| Melting temperature | 1042 K | |||
| Boiling temperature | 1657 K | |||
| Beats heat of fusion | 9.20 kJ / mol | |||
| Beats heat of vaporization | 144 kJ / mol | |||
| Molar heat capacity | 26.79 [2] J / (K Β· mol) | |||
| Molar volume | 33.7 cmΒ³ / mol | |||
| The crystal lattice of a simple substance | ||||
| Lattice structure | cubic face-centered | |||
| Lattice options | 6.080 Γ | |||
| Debye temperature | [3] 147 K | |||
| Other characteristics | ||||
| Thermal conductivity | (300 K) (35.4) W / (mK) | |||
| CAS Number | ||||
| 38 | Strontium |
Sr | |
| 5s 2 | |
Content
- 1 History and origin of the name
- 2 Being in nature
- 2.1 Deposits
- 3 Getting
- 4 Physical properties
- 5 Chemical properties
- 6 Application
- 6.1 Metallurgy
- 6.2 Metallothermy
- 6.3 Magnetic materials
- 6.4 Pyrotechnics
- 6.5 Nuclear power
- 6.6 High temperature superconductivity
- 6.7 Vacuum electronic devices
- 6.8 Chemical current sources
- 6.9 Medicine
- 7 Biological role
- 7.1 Effect on the human body
- 8 Isotopes
- 8.1 Strontium-90
- 9 notes
- 10 Links
History and origin of the name
A new element was found in the mineral strontianite , found in 1764 in a lead mine near the Scottish village of ( English Strontian , Gaelic. Sròn an t-Sìthein ), which later gave the name to the new element. The presence of new metal oxide in this mineral was established in 1787 by William Kruykshenk and Ader Crawford . Allocated in pure form by Sir Humphrey Davy in 1808 .
Being in nature
Free strontium does not occur due to its high chemical activity. It is part of about 40 minerals. Of these, the most important is celestin SrSO 4 (51.2% Sr). Strontianite SrCO 3 (64.4% Sr) is also mined. These two minerals are of industrial importance. Most often, strontium is present as an impurity in various calcium minerals.
Other strontium minerals include:
- SrAl 3 (AsO 4 ) SO 4 (OH) 6 - kemmlicit ;
- Sr 2 Al (CO 3 ) F 5 - stenonite ;
- SrAl 2 (CO 3 ) 2 (OH) 4 Β· H 2 O - strontiocresserite ;
- SrAl 3 (PO 4 ) 2 (OH) 5 Β· H 2 O β goyasite ;
- Sr 2 Al (PO 4 ) 2 OH - hardened ;
- SrAl 3 (PO 4 ) SO Β· 4 (OH) 6 - swanbergite ;
- Sr (AlSiO 4 ) 2 - slosonite ;
- Sr (AlSi 3 O 8 ) 2 Β· 5H 2 O - brewsterite ;
- Sr 5 (AsO 4 ) 3 F β ferermorite ;
- Sr 2 (B 14 O 23 ) Β· 8H 2 O β strontium - jinorite ;
- Sr 2 (B 5 O 9 ) Cl Β· H 2 O β strontiochilguardite ;
- SrFe 3 (PO 4 ) 2 (OH) 5 Β· H 2 O β lusunite ;
- SrMn 2 (VO 4 ) 2 4H 2 O β santafeite ;
- Sr 5 (PO 4 ) 3 OH - whitewash ;
- SrV (Si 2 O 7 ) - charadaite ;
- SrB 2 Si 2 O 8 - pecovite [5] .
According to the level of physical prevalence in the earth's crust, strontium takes 23rd place - its mass fraction is 0.014% (in the lithosphere - 0.045%). The molar fraction of metal in the earth's crust is 0.0029%.
Strontium is found in sea water (8 mg / l) [6] .
Deposits
Famous deposits in California, Arizona ( USA ); New Granada Turkey, Iran, China, Mexico, Canada, Malawi [7] .
Deposits of strontium ores have been discovered in Russia, but are currently not being developed: Blue stones (Dagestan), Mazuevskoye (Perm Territory), Tabolskoye (Tula Oblast), as well as deposits in Buryatia, Irkutsk Oblast, Krasnoyarsk Territory, Yakutia and the Kuril Islands [ 8] [9] .
Getting
There are three methods for producing metallic strontium:
- thermal decomposition of certain compounds;
- electrolysis ;
- reduction of oxide or chloride .
The main industrial method for producing metallic strontium is the thermal reduction of its aluminum oxide. Next, the obtained strontium is purified by distillation.
The electrolytic production of strontium by electrolysis of a melt of a mixture of SrCl 2 and NaCl is not widespread due to the low current efficiency and contamination of strontium by impurities.
During thermal decomposition of strontium hydride or nitride, finely dispersed strontium is formed, which is prone to light ignition.
Physical Properties
Strontium - a soft silver-white metal, has ductility and ductility, is easily cut with a knife.
Polymorphic - three of its modifications are known. Up to 215 Β° Π‘, the cubic face-centered modification (Ξ±-Sr) is stable, between 215 and 605 Β° Π‘ - hexagonal (Ξ²-Sr), above 605 Β° Π‘ - the cubic volume-centered modification (Ξ³-Sr).
Melting point: 768 Β° C, boiling point: 1390 Β° C.
Chemical Properties
Strontium always exhibits an oxidation state of +2 in its compounds. By its properties, strontium is close to calcium and barium, occupying an intermediate position between them.
In the electrochemical series of stresses, strontium is among the most active metals (its normal electrode potential is β2.89 V). Vigorously reacts with water to form hydroxide :
It interacts with acids, displaces heavy metals from their salts. With concentrated acids (H 2 SO 4 , HNO 3 ) reacts weakly.
Strontium metal rapidly 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.
Vigorously reacts with non-metals - sulfur , phosphorus , halogens . It interacts with hydrogen (above 200 Β° C), nitrogen (above 400 Β° C). Practically does not react with alkalis.
At high temperatures it reacts with CO 2 to form carbide :
Slightly soluble strontium salts with anions Cl - , I - , NO 3 - . Salts with anions F - , SO 4 2β , CO 3 2β , PO 4 3β are poorly soluble.
Due to the high chemical activity of strontium, it is stored in a closed glass container under a layer of kerosene.
Application
The main applications of strontium and its chemical compounds are the radio-electronic industry, pyrotechnics, metallurgy, and the food industry.
Metallurgy
Strontium is used for alloying copper and some of its alloys, for introduction into lead-acid alloys, for desulfurization of cast iron, copper and steel.
Metallothermy
Strontium with a purity of 99.99β99.999% is used to reduce uranium.
Magnetic materials
Solid strontium ferrites are widely used as materials for the production of permanent magnets .
Pyrotechnics
In pyrotechnics carbonate , nitrate , strontium perchlorate are used to color the flame in carmine- red color . Magnesium-strontium alloy has the strongest pyrophoric properties and is used in pyrotechnics for incendiary and signal compositions.
Nuclear Power
Strontium uranate plays an important role in the production of hydrogen (strontium-uranate cycle, Los Alamos, USA) by the thermochemical method (atomic hydrogen energy), and, in particular, methods are being developed for the direct fission of uranium nuclei in strontium uranate to produce heat during water decomposition on hydrogen and oxygen.
High Temperature Superconductivity
Strontium oxide is used as a component of superconducting ceramics.
Vacuum Electronic Devices
Strontium oxide , as part of a solid solution of oxides of other alkaline earth metals - barium and calcium ( BaO , CaO), is used as an active layer of indirect cathodes in vacuum electronic devices .
Chemical current sources
Strontium fluoride is used as a component of solid-state fluorionic rechargeable batteries with high energy intensity and energy density.
Strontium alloys with tin and lead are used for casting battery collectors. Strontium- cadmium alloys for anodes of galvanic cells.
Medicine
An isotope with an atomic mass of 89, having a half-life of 50.55 days, is used (in the form of chloride) as an antitumor agent [10] [11] .
Biological role
Effect on the human body
The effects of natural strontium (non-radioactive, low toxicity and, moreover, widely used to treat osteoporosis) and radioactive isotopes of strontium should not be confused [12] .
Natural strontium is an integral part of microorganisms, plants and animals. Strontium is an analogue of calcium, so it is most effectively deposited in bone tissue. In soft tissues less than 1% is retained. Strontium accumulates with great speed in the body of children up to four years of age, when there is an active formation of bone tissue. Strontium metabolism changes with some diseases of the digestive system and the cardiovascular system.
Routes of entry:
- water (the maximum permissible concentration of strontium in water in the Russian Federation is 8 mg / l, and in the USA - 4 mg / l [12] )
- food (tomatoes, beets, dill, parsley, radish, radish, onions, cabbage, barley, rye, wheat)
- intratracheal intake
- through the skin (cutaneous)
- inhalation (via the lungs)
- people whose work is associated with strontium (in medicine, radioactive strontium is used as applicators in the treatment of skin and eye diseases.
Main scopes:
- natural strontium - radio-electronic industry, pyrotechnics, metallurgy, metallothermy, food industry, production of magnetic materials;
- radioactive - the production of atomic electric batteries, atomic hydrogen energy, radioisotope thermoelectric generators and more).
The effect of non-radioactive strontium is extremely rare and only when exposed to other factors (calcium and vitamin D deficiency, malnutrition, disturbances in the ratio of trace elements such as barium, molybdenum, selenium and others). Then it can cause in children "strontium rickets" and "level disease" - damage and deformation of joints, growth retardation and other disorders.
Radioactive strontium almost always negatively affects the human body. Deposited in bones, it irradiates bone tissue and bone marrow, which increases the risk of malignant bone tumors, and when a large amount is received, it can cause radiation sickness.
Isotopes
In nature, strontium is found as a mixture of four stable isotopes 84 Sr (0.56 (2)%), 86 Sr (9.86 (20)%), 87 Sr (7.00 (20)%), 88 Sr (82 , 58 (35)%) [13] . Percentages are indicated by the number of atoms. Radioactive isotopes of strontium with a mass number from 73 to 105 are also known. Light isotopes (up to and including 85 Sr, as well as 87m Sr isomer ) experience electron capture, decaying into the corresponding rubidium isotopes. Heavy isotopes, starting from 89 Sr, experience Ξ² - decay , passing into the corresponding yttrium isotopes. The most long-lived and practically important among the radioactive isotopes of strontium is 90 Sr.
Strontium-90
The strontium isotope 90 Sr is radioactive with a half-life of 28.78 years . 90 Sr undergoes Ξ² - decay , turning into radioactive 90 Y (half-life 64 hours), which, in turn, decays into stable zirconium-90. The complete decay of strontium-90, which has entered the environment, will occur only after a few hundred years.
90 Sr is formed during nuclear explosions and inside a nuclear reactor during its operation. The formation of strontium-90 occurs both directly as a result of fission of uranium and plutonium nuclei and as a result of beta decay of short-lived nuclei with mass number A = 90 (in the chain 90 Se β 90 Br β 90 Kr β 90 Rb β 90 Sr ) formed by division.
It is used in the production of radioisotope energy sources in the form of strontium titanate (density 4.8 g / cmΒ³ , and energy release - about 0.54 W / cmΒ³ ).
Notes
- β 1 2 Meija J. et al. Atomic weights of the elements 2013 (IUPAC Technical Report ) // Pure and Applied Chemistry . - 2016. - Vol. 88, no. 3 . - P. 265β291. - DOI : 10.1515 / pac-2015-0305 .
- β Editorial board: N. S. Zefirov (chap. Ed.). Chemical encyclopedia: in 5 volumes. - Moscow: Big Russian Encyclopedia, 1995. - V. 4. - P. 441. - 639 p. - 20,000 copies. - ISBN 5-85270-092-4.
- β Strontium on Integral Scientist Modern Standard Periodic Table
- β Mendeleev's table on the IUPAC website.
- β GEOCHI RAS - Igor Viktorovich Pekov . geokhi.ru. Date of treatment May 11, 2016.
- β JP Riley and Skirrow G. Chemical Oceanography V. I, 1965
- β Rubidium - Properties of chemical elements
- β A. M. Portnov. Forgotten element of strategic importance . Independent newspaper (09.28.2011).
- β http://www.kscnet.ru/ivs/publication/volc_day/2017/art55.pdf
- β ABC Magazine - Strontium-89 Chloride - Strontium Chloride [89Sr]
- β Thesis on the topic "Modern tactics of systemic radiotherapy with strontium chloride-89 in the complex treatment of patients with metastatic bone damage." Abstract on special ...
- β 1 2 Toxicological data of strontium
- β Meija J. et al. Isotopic compositions of the elements 2013 (IUPAC Technical Report ) // Pure and Applied Chemistry . - 2016. - Vol. 88 , no. 3 . - P. 293-306 . - DOI : 10.1515 / pac-2015-0503 .