strontium [from Strontian, a Scottish town], a metallic chemical element; symbol Sr; at. no. 38; at. wt. 87.62; m.p. 769°C; b.p. 1,384°C; sp. gr. 2.6 at 20°C; valence +2. Strontium is a soft, silver-yellow metal with three allotropic crystalline forms (see allotropy ). It is an alkaline-earth metal ; in its physical and chemical properties it resembles calcium and barium, the elements above and below it in Group 2 of the periodic table . Since strontium reacts vigorously with water and quickly tarnishes in air, it must be stored out of contact with air and water. Among its compounds are the oxide strontia, SrO; peroxide, SrO ₂  ; hydroxide, Sr(OH) ₂  ; nitrate, Sr(NO ₃ ) ₂  ; the carbonate strontianite, SrCO ₃  ; the sulfate celestite, SrSO ₄  ; carbide, SrC ₂  ; and halides, SrBr ₂ , SrCl ₂ , SrF ₂ , and SrI ₂ . Celestite and strontianite are the chief ores of strontium. The metal may be prepared by electrolysis of fused strontium chloride; small amounts of the metal are used in semiconductor devices. Although strontium has uses similar to those of calcium and barium, it is rarely employed because of its higher cost. Principal uses of strontium compounds are in pyrotechnics (chiefly the nitrate) and in greases (the hydroxide). In fireworks and signal flares strontium compounds add a bright red or crimson color to the flame. Naturally occurring strontium is a mixture of four stable isotopes. Twelve unstable isotopes exist; the most stable of these is the radioactive isotope strontium-90 (half-life 28.1 years), which is the chief immediate hazard in fallout . As a result of atmospheric nuclear tests, strontium-90 is dispersed in varying concentrations throughout the earth's atmosphere and soil. Because of its chemical similarity to calcium, it is readily taken up in the tissues of plants and animals; it may enter the human food supply, mainly in milk. It is particularly dangerous for growing children as it is easily deposited in the bones and is believed to induce bone cancer and leukemia. Strontium-90 also has some uses in luminous signs and in nuclear batteries. Strontium was first recognized as distinct from barium in 1790 by A. Crawford in a sample of its carbonate from a mine near Strontian, Scotland; his finding was later confirmed by T. C. Hope, M. H. Klaproth, and others. It was first isolated by electrolysis in 1808 by Humphry Davy.

Strontium

melting point: 769°C
boiling point: 1,383°C
density: 2.54 g/cm³
most common ions: Sr²⁺

Strontium is the thirty-eighth element in the Periodic Table and the sixteenth most abundant element in Earth's crust. It was first recognized by Adair Crawford in 1790, who named the substance "strontianite," after the Scottish town of Strontian where samples were originally obtained. However, it was Sir Humphrey Davy who actually isolated strontium in elemental form in 1808, using his electrolysis apparatus.

There are four stable isotopes of strontium that are found naturally. In addition there are about twenty radioactive isotopes, including strontium-90, a deadly by-product of nuclear -bomb detonations. The natural forms of strontium are relatively nontoxic. Similar to calcium both physically and chemically, elemental strontium is a soft, shiny metal . Like calcium and other alkaline earth metals, it is easily oxidized and thus not found naturally in its free elemental state. Instead, it almost always is found in the +2 oxidation state, forming such compounds as strontium oxide (SrO), strontium sulfate (SrSO₄, from the mineral celestite), strontium carbonate (SrCO₃, from the mineral strontianite), and strontium chloride (SrCl₂). Strontium nitrate, Sr(NO₃)₂, is used to produce the brilliant red color seen in some fireworks and signal flares and is also used in making "tracer bullets" that can be seen when fired at night. Other strontium compounds are sometimes used in the manufacture of special glasses. Yet overall, strontium is not a very important element industrially or commercially.

see also Davy, Humphry

David A. Dobberpuhl

Bibliography

Heiserman, David L. (1992). Exploring Chemical Elements and Their Compounds. Blue Ridge Summit, PA: Tab Books.

Krebs, Robert E. (1998). The History and Use of Our Earth's Chemical Elements: A Reference Guide. Westport, CT: Greenwood Press.

strontium (stron-tiŭm) n. a yellow metallic element, absorption of which causes bone damage when its atoms displace calcium in bone. Symbol: Sr. strontium-89 a radioactive isotope used in the treatment of metastatic carcinoma for the relief of pain due to bone metastases. strontium-90 a radioactive isotope used in radiotherapy for the contact therapy of skin and eye tumours and in radioimmunotherapy in combination with monoclonal antibodies.

stron·ti·um / ˈstränchēəm; -tēəm/ • n. the chemical element of atomic number 38, a soft, silver-white metal of the alkaline earth series. Its salts are used in fireworks and flares because they give a brilliant red light. (Symbol: Sr)

strontium Symbol Sr. A soft yellowish metallic element. The isotope strontium–90 is present in radioactive fallout (half-life 28 years), and can be metabolized with calcium so that it collects in bone.

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