Strontium - Element information, properties and uses | Periodic Table Chemistry in its element: strontium (Promo) You're listening to Chemistry in its element brought to you by Chemistry World, the magazine of the Royal Society of Chemistry. (End promo) Chris Smith Hello! This week, vegetarian gladiators, red fireworks and a mineral mistaken for barium; they are all under strontium's spotlight. Here's Richard Van Noorden. Richard Van Noorden In 1787, an intriguing mineral came to Edinburgh from a Lead mine in a small village on the shores of Loch Sunart, Argyll, in the western highlands of Scotland. At that time, the stuff was thought to be some sort of Barium compound. It was three year's later that Scott's Irish chemist, Adair Crawford, published a paper claiming that the mineral held a new species including a new chemical element. Other chemists, such as Edinburgh's Thomas Hope later prepared a number of compounds with the element, noting that it caused the candle's flame to burn red, while Barium compounds gave a green colour.

And in 1808, Humphry Davy in London isolated the soft, silvery metal of the new element using electrolysis. The Scottish village was called Strontian, the mineral found there, strontianite and the new element strontium. So, it seems there never was an eminent professor, Stront, commemorated by element number 38. Today, whenever you see a firework light up in brilliant crimson or a red flare smoking its way around a football stadium, you're looking at the light emitted from electrons transiting between energy levels in nitrate or carbonate salts as strontium. Strontium is most famous for that red glow in a flame, but as a metal it behaves like its reactive group II neighbours, beryllium, magnesium, calcium and barium. It's soft and silvery when freshly cut, but this sheen quickly turns yellow when exposed to air, as the metal readily reacts to form oxides; unlike other reactive alkaline earth metals, natural strontium is always found locked away in mineral compounds.

Apart from the previously mentioned strontianite, which we know as strontium carbonate, there is also the beautiful sky blue celestite, strontium sulphate, which was discovered in Gloucestershire in 1799, where the locals were using it as gravel for paths in ornamental gardens. Apart from colouring fireworks, we don't have much call nowadays for strontium compounds. Strontium carbonate notably is found in cathode ray tubes in old television sets. One of strontium's isotopes Strontium-90 has a more sinister reputation. It's a radioactive beta emitter, produced by nuclear fission with a half-life of 29 years. Created by nuclear tests from 1945 to the early 1970s, strontium-90 made its way from the air to grassland, cow stomachs, dairy products and as 1950's studies showed into children's milk teeth. It collects in bones too, being of a similar size to its group II neighbour, calcium ions. The nuclear reactor accident at Chernobyl in 1986 also threw strontium-90 into the air.

Nowadays, it's used as a radioactive tracer in cancer therapy. Still strontium's close relation to calcium has made it a modern treatment for treating osteoporosis as the salt strontium ranelate, using non-radioactive isotopes, of course. Because strontium ions are roughly the same size as calcium ions, they bind tightly to calcium sensing receptors. It seems that this stimulates the formation of new bones and prevents old bone from being broken down. And tracing strontium isotope levels in bone has allowed analytical chemists to come up with all sorts of conclusions about our past ancestor's diets, knowing that plants tend to be higher in natural strontium than meat. In 2007, for instance, Austrian researchers hit headlines by comparing strontium and zinc levels to support the hypothesis that Roman gladiators were vegetarians who ate mainly barley, beans and dried fruits. Chris Smith Chemistry World's Richard Van Noorden wrestling gladiator style with the story of strontium. Next time, we've heard of running through treacle, but what about this proposition. Fred Campbell Could a man walk across a swimming pool filled with Mercury?

Don't ask me how the conversation had reached this point, but being surrounded by friends, who would, it is fair to say, describe themselves as science illiterate, I knew it was up to me, the token scientist around the table, to give the definitive answer. "No." I confidently said, adding rather smugly, "it is nowhere near dense enough." The next morning I was rudely awakened by my ringing mobile; not for the first time, I was wrong! Chris Smith And you can find out exactly how wrong Fred Campbell was at his dinner party when he unlocks the chemical secrets of quick silver, otherwise known as mercury on next week's Chemistry in its element. I hope you can join us. I'm Chris Smith, thanks for listening. Goodbye! (Promo) Chemistry in its element is brought to you by the Royal Society of Chemistry and produced by thenakedscientists.com . There's more information and other episodes of Chemistry in its element on our website at chemistryworld.org/elements . (End promo) Strontium | Elements Wiki | Fandom powered by Wikia Share Strontium is a chemical element with symbol Sr and atomic number 38.

An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when it is exposed to air. Strontium has physical and chemical properties similar to those of its two neighbors calcium and barium. It occurs naturally in the minerals celestine, putnisite and strontianite. While natural strontium is stable, the synthetic 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years. Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was discovered in 1790 by Adair Crawford and William Cruickshank. The production of sugar from sugar beet was in the 19th century its largest application (see strontian process). At the peak of production of television cathode ray tubes, up to 75 percent of U.S.

strontium consumption was used to make the faceplate glass.[4] With the displacement of cathode ray tubes by other display methods in television sets, consumption of strontium has dramatically declined.[4] Strontium - Wikipedia, the free encyclopedia Strontium Sr is stable with 46 neutrons 85Sr Sr is stable with 48 neutrons 87Sr Sr is stable with 49 neutrons 88Sr Sr is stable with 50 neutrons 89Sr References Strontium ( IPA : /ˈstrɒntiəm/) is a chemical element in the periodic table that has the symbol Sr and the atomic number 38. An alkaline earth metal , strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite . The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.

Contents [ edit ] Notable characteristics Due to its extreme reactivity to air, this element occurs naturally only in compounds with other elements, as in the minerals strontianite and celestite. Strontium is a bright silvery metal that is softer than calcium and even more reactive in water , which strontium decomposes on contact with to produce strontium hydroxide and hydrogen gas. It burns in air to produce both strontium oxide and strontium nitride , but since it does not react with nitrogen below 380°C it will only form the oxide spontaneously at room temperature. It should be kept under kerosene to prevent oxidation ; freshly exposed strontium metal rapidly turns a yellowish color with the formation of the oxide. Finely powdered strontium metal will ignite spontaneously in air. Volatile strontium salts impart a crimson color to flames , and these salts are used in pyrotechnics and in the production of flares . Natural strontium is a mixture of four stable isotopes .

[ edit ] Applications As a pure metal strontium is being used in strontium 90%-aluminium 10% alloys of an eutectic composition for the modification of aluminium-silicon casting alloys. The primary use for strontium compounds is in glass for color television cathode ray tubes to prevent X-ray emission. Other uses: 89Sr is the active ingredient in Metastron, a radiopharmaceutical used for bone pain secondary to metastatic prostate cancer . The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis . This localization focuses the radiation exposure on the cancerous lesion. 90Sr has been used as a power source for radioisotope thermoelectric generators (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the grade of 90Sr used in RTGs, which is strontium fluoride ). [1] However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu , another RTG fuel.

The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste . 90Sr is also used in cancer therapy. Its beta emission and long half-life is ideal for superficial radiotherapy . Strontium is one of the constituents of AJ62 alloy, a durable magnesium alloy used in car and motorcycle engines by BMW . 87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments. Dasch (1969) showed that surface sediments of the deep Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses. A good example of a fluvial system to which Sr isotope ratio studies have been frequently employed is the River Nile (Krom et al, 1999; Krom et al, 2002; Talbot et al. 2000).

Due to the vastly differing ages of the rocks that constitute the majority of the Blue and White Nile catchment areas the changing provenance of sediment reaching the River Nile delta, and East Mediterranean Sea beyond, can be discerned through Sr isotopic studies. This information is useful as it can elicit information regarding palaeoclimate change. [ edit ] History The mineral strontianite is named after the Scottish village of Strontian having been discovered in the lead mines there in 1787 . [2] Adair Crawford recognized it as differing from other barium minerals in 1790 . Strontium itself was discovered in 1798 by Thomas Charles Hope , and metallic strontium was first isolated by Sir Humphry Davy in 1808 using electrolysis . Strontium was among the radioactive materials released by the 1957 Windscale fire . [ edit ] Occurrence Strontium output in 2005 In 2005, China was the top producer of strontium with almost two-thirds world share followed by Spain and Mexico, reports the British Geological Survey .

Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development. The metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride : Sr2+ + 2 e- → Sr 2 Cl- → Cl2 ( g ) + 2 e- Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. The largest commercially exploited deposits are found in England .

Main article: Isotopes of strontium The alkali earth metal strontium has four stable, naturally occurring isotopes : 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic ; it is produced by decay from the radioactive alkali metal 87 Rb , which has a half-life of 4.88 × 1010 years. Thus, there are two sources of 87Sr in any material: that formed during primordial nucleo-synthesis along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium , it readily substitutes for Ca in minerals . Sixteen unstable isotopes are known to exist.

Of greatest importance is 90Sr with a half-life of 28.78 years. It is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone , preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP ( Systems for Nuclear Auxiliary Power ) devices. These devices hold promise for use in spacecraft , remote weather stations, navigational buoys, etc, where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. [ edit ] Precautions In its pure form strontium is extremely reactive with air and spontaneously combusts. It is therefore considered to be a fire hazard . [ edit ] Effect on the human body The human body absorbs strontium as if it were calcium . Due to the elements being sufficiently similar chemically, the stable forms of strontium do not pose a significant health threat, but the radioactive 90Sr can lead to various bone disorders and diseases , including bone cancer .

The strontium unit is used in measuring radioactivity from absorbed 90Sr. An innovative drug made by combining strontium with ranelic acid has aided in bone growth, boosted bone density and lessened vetrebral, peripheral and hip fractures . [3] [4] Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass. It means that strontium ranelate creates new and strong bone. Strontium ranelate (marketed under the trade names Protelos, Osseor, Protos, Bivalos, Protaxos, Ossum) is registered for treatment of osteoporosis in many countries all over the world. Strontium ranelate has been shown to strengthen bones, according presentations given the IOF World Congress on Osteoporosis, in June of 2006. It also reduced bone resorbtion.

Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It needs to be prescribed by a doctor, delivered by a pharmacist and requires a strict medical supervision. Currently, (early 2007) it is not available in Canada or the United States. Several other salts of strontium such as strontium citrate or strontium carbonate are often presented as natural therapies and sold at a dose that is several hundred times higher than the usual strontium intake. Despite the lack of strontium deficit referenced in the medical literature and the lack of information about possible toxicity of strontium supplementation, such compounds can still be sold in the United States under the Dietary Supplements Health and Education Act of 1994. However, their long-term safety and efficacy have never been evaluated on humans using large-scale medical trials. Such compounds should not be administered to humans before further studies are conducted. Los Alamos National Laboratory – Strontium . Retrieved on August 5 , 2005 . Dasch, J. (1969). Strontium isotopes in weathering profiles, deep-sea sediments, and sedimentary rocks.

Geochimica et Cosmochimica Acta, Vol. 33, pp. 1521-1552. Krom et al. (1999). The characterisation of Saharan Dusts and Nile particulate matter in surface sediments from the Levantine basin using Sr isotopes. Marine Geology, Vol. 155, pp. 319-330. Krom et al. (2002). Nile River sediment fluctuations over the past 7000 yr and their key role in sapropel development. Geology, Vol. 30, pp. 71-74. Talbot et al., (2000). Strontium isotope evidence for late Pleistocene reestablishment of an integrated Nile drainage network. Geology, Vol. 28, pp. 343-346.

Strontium Strontium Ba Periodic Table - Extended Periodic Table General Name , Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Atomic mass 87.62 (1) g/mol Electron configuration [ Kr ] 5s2 Electrons per shell 2, 8, 18, 8, 2 Physical properties Phase solid Density (near r.t.) 2.64 g·cm−3 Liquid density at m.p.

6.980 g·cm−3 Melting point 1050 K (777 ° C, 1431 ° F) Boiling point 1655 K (1382 ° C, 2520 ° F) Heat of fusion 7.43 kJ·mol−1 Heat of vaporization 136.9 kJ·mol−1 Heat capacity (25 °C) 26.4 J·mol−1·K−1 Vapor pressure Atomic properties Crystal structure cubic face centered Oxidation states 2 (strongly basic oxide) Electronegativity 0.95 (Pauling scale) Ionization energies ( more) 1st: 549.5 kJ·mol−1 2nd: 1064.2 kJ·mol−1 3rd: 4138 kJ·mol−1 Atomic radius 200 pm Atomic radius (calc.) 219 pm Covalent radius 192 pm Miscellaneous Magnetic ordering paramagnetic Electrical resistivity (20 °C) 132 nΩ·m Thermal conductivity (300 K)

 35.4 W·m−1·K−1 Thermal expansion (25 °C) 22.5 µm·m−1·K−1 Shear modulus 6.1 GPa Poisson ratio 0.28 Mohs hardness 1.5 CAS registry number 7440-24-6 Selected isotopes Main article: Isotopes of strontium iso Sr is stable with 46 neutrons 85Sr Sr is stable with 48 neutrons 87Sr Sr is stable with 49 neutrons 88Sr Sr is stable with 50 neutrons 89Sr 90 Y References Strontium ( IPA: /ˈstrɒntiəm/) is a chemical element in the periodic table that has the symbol Sr and the atomic number 38.

An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestite and strontianite. The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years. Notable characteristics Due to its extreme reactivity to air, this element occurs naturally only in compounds with other elements, as in the minerals strontianite and celestite. Strontium is a bright silvery metal that is softer than calcium and even more reactive in water , which strontium decomposes on contact to produce strontium hydroxide and hydrogen gas. It burns in air to produce both strontium oxide and strontium nitride, but since it does not react with nitrogen below 380°C it will only form the oxide spontaneously at room temperature. It should be kept under kerosene to prevent oxidation; freshly exposed strontium metal rapidly turns a yellowish colour with the formation of the oxide. Finely powdered strontium metal will ignite spontaneously in air.

Volatile strontium salts impart a crimson colour to flames , and these salts are used in pyrotechnics and in the production of flares. Natural strontium is a mixture of four stable isotopes. Applications At present the primary use for strontium is in glass for colour television cathode ray tubes. Other commercial uses: Production of ferrite magnets and refining zinc . Strontium titanate has an extremely high refractive index and an optical dispersion greater than that of diamond , making it useful in a variety of optics applications. Strontium titanate has been cut into gemstones, in particular for its use as diamond simulant . However, it is very soft and easily scratches so it is rarely used. Strontium is also used in fireworks for red colour. Strontium aluminate is used as a bright phosphor with long persistence of phosphorescence. Strontium chloride is sometimes used in toothpastes for sensitive teeth. One popular brand includes 10% strontium chloride hexahydrate by weight. Strontium oxide is sometimes used to improve the quality of some pottery glazes.

89Sr is the active ingredient in Metastron, a radiopharmaceutical used for bone pain secondary to metastatic prostate cancer . The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis. This localization focuses the radiation exposure on the cancerous lesion. 90Sr has been used as a power source for RTGs. 90Sr produces about 0.93 watts of heat per gram (it is lower for the grade of 90Sr used in RTGs, which is strontium fluoride). However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu, another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste. 90Sr is also used in cancer therapy. Its beta emission and long half-life is ideal for superficial radiotherapy. Strontium is also commonly used in aerosol paint, such as the Spanish Montana (Montana Hardcore). This is one of the most likely sources of exposure to the public.

History The mineral strontianite is named after the Scottish village of Strontian having been discovered in the lead mines there in 1787 - see Murray (1977). Adair Crawford recognized it as differing from other barium minerals in 1790. Strontium itself was discovered in 1798 and metallic strontium was first isolated by Sir Humphry Davy in 1808 using electrolysis. Strontium was among the radioactive materials released by the 1957 Windscale fire. Occurrence Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (Sr S O 4) and the carbonate strontianite (Sr C O3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development.

The metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride: Sr2+ + 2 e- → Sr 2 Cl- → Cl2 ( g ) + 2 e- Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. Strontium metal (98% pure) in January 1990 cost about $5/oz. The largest commercially exploited deposits are found in England . Isotopes The alkali earth metal strontium has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87 Rb , which has a half-life of 4.88 × 1010 years.

Thus, there are two sources of 87Sr in any material: that formed during primordial nucleo-synthesis along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium , it readily substitutes for Ca in minerals . Sixteen unstable isotopes are known to exist. Of greatest importance is 90Sr with a half-life of 28.78 years. It is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP ( Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc, where a lightweight, long-lived, nuclear-electric power source is required.

The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. Precautions In its pure form strontium is extremely reactive with air and spontaneously combusts. It is therefore considered to be a fire hazard. Effect on the human body The human body absorbs strontium as if it were calcium . Due to the elements being sufficiently similar chemically, the stable forms of strontium do not pose a significant health threat, but the radioactive 90Sr can lead to various bone disorders and diseases, including bone cancer. The strontium unit is used in measuring radioactivity from absorbed 90Sr. An experimental drug made by combining strontium with ranelic acid has aided in bone growth, boosted bone density and lessened fractures. (El-Hajj, 2004) Women receiving the drug showed a 6.8% increase in bone density. Women receiving a placebo had a 1.3% decrease. (Meunier et. al, 2004).

Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half is assumed to be a true increase in bone mineral content. Strontium ranelate is registered for treatment of osteoporosis in Europe at a dose of 2 grams daily. Several naturally occurring strontium compounds have additionally been found to enhance bone growth and density and lessen the incidence of fractures, and efficacy of treatment has not been shown to vary significantly between various strontium compounds. These compounds include strontium lactate (McCaslin et. al, Mayo Clin. 1959;34(13):329-34), strontium citrate (Wright et. al, Tahoma Clin.), strontium carbonate and strontium gluconate (Skoryna et. al, 1984). Retrieved from " " This reference article is mainly selected from the English Wikipedia with only minor checks and changes (see for details of authors and sources) and is available under the Rejuve - Strontium Strontium Overview: Strontium is a chemical element with the symbol Sr and the atomic number 38.

An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite. The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years. Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered. Characteristics Due to its extreme reactivity with oxygen and water, this element occurs naturally only in compounds with other elements, as in the minerals strontianite and celestite. Strontium is a grey/silvery metal that is softer than calcium and even more reactive in water, with which strontium reacts on contact to produce strontium hydroxide and hydrogen gas. It burns in air to produce both strontium oxide and strontium nitride, but since it does not react with nitrogen below 380°C it will only form the oxide spontaneously at room temperature.

It should be kept under a liquid hydrocarbon such as mineral oil or kerosene to prevent oxidation; freshly exposed strontium metal rapidly turns a yellowish color with the formation of the oxide. Finely powdered strontium metal will ignite spontaneously in air at room temperature. Volatile strontium salts impart a crimson color to flames, and these salts are used in pyrotechnics and in the production of flares. Natural strontium is a mixture of four radiostable isotopes Compounds Category:Strontium compounds Ferrite magnets and refining zinc. Strontium titanate has an extremely high refractive index and an optical dispersion greater than that of diamond, making it useful in a variety of optics applications. This quality has also led to it being cut into gemstones, in particular as a diamond simulant. However, it is very soft and easily scratches so it is rarely used. Strontium carbonate, strontium nitrate, and strontium sulfate are commonly used in fireworks for red color sometimes for other colors too. Strontium aluminate is used as a bright phosphor with long persistence of phosphorescence. Strontium chloride is sometimes used in toothpastes for sensitive teeth.

One popular brand includes 10% total strontium chloride hexahydrate by weight. Strontium oxide is sometimes used to improve the quality of some pottery glazes. Strontium ranelate is used in the treatment of osteoporosis. It is a prescription drug in the EU, but not in the USA. Strontium barium niobate is used in large scale outdoors Holgraphic displays as a "screen". When projected with blue laser light images are 3-D and very realistic. Isotopes Main article: Isotopes of strontium Strontium has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87Rb, which has a half-life of 4.88 × 1010 years.

Thus, there are two sources of 87Sr in any material: that formed in stars along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium, it readily substitutes for Ca in minerals. Sixteen unstable isotopes are known to exist. Of greatest importance are 90Sr with a half-life of 28.78 years and 89Sr with a half-life of 50.5 days. 90Sr is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxiliary Power) devices.

These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc, where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. 90Sr confined inside a concave silver plaque is also used for the medical treatment of a resected pterygium. 89Sr is a short-lived artificial radioisotope which is used in the treatment of bone cancer. In circumstances where cancer patients have widespread and painful bony metastases (secondaries), the administration of 89Sr results in the delivery of radioactive emissions (beta particles in this case) directly to the area of bony problem (where calcium turnover is greatest). The 89Sr is manufactured as the chloride salt (which is soluble), and when dissolved in normal saline can be injected intravenously. Typically, cancer patients will be treated with a dose of 150 MBq. The patient needs to take precautions following this because their urine becomes contaminated with radioactivity, so they need to sit to urinate and double flush the toilet.

The beta particles travel about 3.5mm in bone (energy 0.583 MeV) and 6.5mm in tissue, so there is no requirement to isolate patients who have been treated except to say they should not have any one (especially young children) sitting in their laps for 10–40 days[citation needed]. The variation in time results from the variable clearing time for 89Sr which depends on renal function and the number of bony metastases. With a lot of bony metastases, the entire 89Sr dose can be taken up into bone and so the entire radioactivity is retained to decay over a 50.5 day half-life. However, where there are few bony metastases, the large proportion of 89Sr not taken up by the bone will be filtered by the kidney, so that the effective half-life (a combination of the physical and biological half-life) will be much shorter.

History Strontium is named after the Scottish village of Strontian, having been discovered in the ores taken from the lead mines .In 1790, Adair Crawford, a physician engaged in the preparation of barium, recognised that the Strontian ores exhibited different properties to those normally seen with other "heavy spars" sources. This allowed him to conclude "... it is probable indeed, that the scotch mineral is a new species of earth which has not hitherto been sufficiently examined". The new mineral was named strontites in 1793 by Thomas Charles Hope, a professor of medicine at the University of Glasgow. He confirmed the earlier work of Crawford and recounted: " ... Considering it a peculiar earth I thought it necessary to give it an name. I have called it Strontites, from the place it was found; a mode of derivation in my opinion, fully as proper as any quality it may possess, which is the present fashion". The element was eventually isolated by Sir Humphry Davy in 1808 by the electrolysis of a mixture containing strontium chloride and mercuric oxide, and announced by him in a lecture to the Royal Society on 30 June 1808.

In keeping with the naming of the other alkaline earths, he changed the name to strontium. Occurrence According to the British Geological Survey, China was the top producer of strontium in 2007, with over two-thirds world share, followed by Spain, Mexico, Turkey, Argentina and Iran. Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development.

The metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride: Sr2+ + 2 e− → Sr 2 Cl− → Cl2 (g) + 2 e− Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. The largest commercially exploited deposits are found in England. Applications As a pure metal strontium is used in strontium 90%-aluminium 10% alloys of an eutectic composition for the modification of aluminium-silicon casting alloys. Strontium is 2% by weight of AJ62 alloy, a durable, creep-resistant magnesium alloy used in car and motorcycle engines by BMW. The primary use for strontium compounds is in glass for colour television cathode ray tubes to prevent X-ray emission.All parts of the CRT tube have to absorb X-rays. In the neck and the funnel of the tube lead glass is used for this purpose, but this type of glass shows a browning effect due to the interaction of the X-rays with the glass.

Therefore the front panel has to use a different glass mixture, in which strontium and barium are the X-ray absorbing materials. The average values for the class mixture determined for a recycling studie in 2005 is 8.5% strontium oxide and 10% barium oxide. Scientific (low quantity) use : Strontium is used in studies of neurotransmitter release in neurons. Like calcium, strontium facilitates synaptic vesicle fusion with the synaptic membrane. But unlike calcium, strontium causes asynchronous vesicle fusion. Therefore, replacing calcium in the culture medium with strontium allows scientists to measure the effects of a single vesicle fusion event, e.g., the size of the postsynaptic response elicited by the neurotransmitter content of a single vesicle. Uses of radioactive strontium isotopes : 89Sr is the active ingredient in Metastron, a radiopharmaceutical used for bone pain secondary to metastatic bone cancer. The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis. This localization focuses the radiation exposure on the cancerous lesion.

90Sr has been used as a power source for radioisotope thermoelectric generators (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the form of 90Sr used in RTGs, which is strontium fluoride). However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu, another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste. 90Sr is also used in cancer therapy. Its beta emission and long half-life is ideal for superficial radiotherapy. Strontium isotopes are measured for various reasons : Since Strontium is so similar to calcium, it is incorporated in the bone. All four stable isotopes are incorporated, in roughly similar proportions as they are found in nature (please see below). However the actual distribution of the isotopes tends to vary greatly from one geographical location to another. Thus analyzing the bone of an individual can help determine the region it came from. This approach helps to identify the ancient migration patterns as well as the origin of commingled human remains in battlefield burial sites.

Strontium thus helps forensic scientists too. 87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments. Dasch (1969) showed that surface sediments of Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses. A good example of a fluvial-marine system to which Sr isotope provenance studies have been successfully employed is the River Nile-Mediterranean system, Due to the differing ages of the rocks that constitute the majority of the Blue and White Nile catchment areas of the changing provenance of sediment reaching the River Nile delta and East Mediterranean Sea can be discerned through Sr isotopic studies. Such changes are climatically controlled in the Late Quaternary. More recently, 87Sr/86Sr ratios have also been used to determine the source of ancient archaeological materials such as timbers and corn in Chaco Canyon, New Mexico. 87Sr/86Sr ratios in teeth may also be used to track animal migrations or in criminal forensics.

Effect on the human body The human body absorbs strontium as if it were calcium. Due to the elements being sufficiently similar chemically, the stable forms of strontium might not pose a significant health threat—in fact, the levels found naturally may actually be beneficial (see below) -- but the radioactive 90Sr can lead to various bone disorders and diseases, including bone cancer. The strontium unit is used in measuring radioactivity from absorbed 90Sr. A recent in-vitro study conducted the NY College of Dental Sciences using strontium on osteoblasts showed marked improvement on bone-building osteoblasts. The drug strontium ranelate, made by combining strontium with ranelic acid, was found to aid bone growth, increase bone density, and lessen vertebral, peripheral and hip fractures. Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass.

Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It needs to be prescribed by a doctor, delivered by a pharmacist, and requires strict medical supervision. Currently (early 2007), it is not available in Canada or the United States. There is a long history of medical research regarding strontium's benefits, beginning in the 1950s. Studies indicate a lack of undesirable side-effects.Several other salts of strontium such as strontium citrate or strontium carbonate are often presented as natural therapies and sold at a dose that is several hundred times higher than the usual strontium intake. Such compounds are sold in the United States under the Dietary Supplements Health and Education Act of 1994. Their long-term safety and efficacy have never been evaluated on humans using large-scale medical trials.

Strontium - 必应 strontium - 必应 © 2016 Microsoft 新的隐私声明和 Cookie 新的法律声明 广告 帮助 反馈 锶 - 必应网典 自然科学 The alkaline earth metal strontium (Sr) has four stable, naturally occurring isotopes: 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). It has a standard ... of strontium?mkt=zh-cn strontium peroxide 别名： 二氧化锶 化学式： SrO2 管制类型： 不管制 相对分子质量： 119.63 化学品类别： 无机物--金属过氧化物 储存： 密封干燥保存 相关词条 过氧化 ...

过氧化锶 Strontium Strontium (1382 ° C , 2520 ° F ) Heat of fusion 7.43 kJ·mol−1 Heat of vaporization 136.9 kJ·mol−1 Heat capacity (25 °C) 26.4 J·mol−1·K−1 Vapor pressure Sr is stable with 46 neutrons 85Sr Sr is stable with 48 neutrons 87Sr Sr is stable with 49 neutrons 88Sr Sr is stable with 50 neutrons 89Sr References Strontium ( pronounced /ˈstrɒntiəm/) is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal , strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite . The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.

Contents 10 References Notable characteristics Due to its extreme reactivity to air, this element occurs naturally only in compounds with other elements, as in the minerals strontianite and celestite . Strontium is a bright silvery metal that is softer than calcium and even more reactive in water, which strontium decomposes on contact with to produce strontium hydroxide and hydrogen gas. It burns in air to produce both strontium oxide and strontium nitride, but since it does not react with nitrogen below 380°C it will only form the oxide spontaneously at room temperature. It should be kept under kerosene to prevent oxidation ; freshly exposed strontium metal rapidly turns a yellowish color with the formation of the oxide. Finely powered strontium metal will ignite spontaneously in air. Volatile strontium salts impart a crimson color to flames, and these salts are used in pyrotechnics and in the production of flares. Natural strontium is a mixture of four stable isotopes .

Applications As a pure metal strontium is being used in strontium 90%-aluminium 10% alloys of an eutectic composition for the modification of aluminium-silicon casting alloys. The primary use for strontium compounds is in glass for colour television cathode ray tubes to prevent X-ray emission. Other uses: 89Sr is the active ingredient in Metastron, a radiopharmaceutical used for bone pain secondary to metastatic prostate cancer. The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis. This localization focuses the radiation exposure on the cancerous lesion. 90Sr has been used as a power source for radioisotope thermoelectric generators (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the grade of 90Sr used in RTGs, which is strontium fluoride ). [2] However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu , another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste.

90Sr is also used in cancer therapy. Its beta emission and long half-life is ideal for superficial radiotherapy . Strontium is one of the constituents of AJ62 alloy, a durable magnesium alloy used in car and motorcycle engines by BMW. 87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments. Dasch (1969) showed that surface sediments of the deep Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses. One good example of a fluvial system to which Sr isotope ratio studies have been frequently employed is the River Nile (Krom et al, 1999; Krom et al, 2002; Talbot et al. 2000). Due to the vastly differing ages of the rocks that constitute the majority of the Blue and White Nile catchment areas the changing provenance of sediment reaching the River Nile delta, and East Mediterranean Sea beyond, can be discerned through Sr isotopic studies.

This information is useful as it can elicit information regarding climate change over geologic time scales. More recently, 87Sr/86Sr ratios have also been used to determine the source of ancient archaeological materials such as timbers and corn in Chaco Canyon, New Mexico (English et al, 2001, Benson et al, 2003). 87Sr/86Sr ratios in teeth may also be used to track animal migrations (Porder et al., 2003) or in criminal forensics. Compounds Ferrite magnets and refining zinc . Strontium titanate has an extremely high refractive index and an optical dispersion greater than that of diamond , making it useful in a variety of optics applications. This quality has also led to it being cut into gemstones , in particular as a diamond simulant . However, it is very soft and easily scratches so it is rarely used. Strontium carbonate , Strontium nitrate, and Strontium sulfate are commonly used in fireworks for red color. Strontium aluminate is used as a bright phosphor with long persistence of phosphorescence . Strontium chloride is sometimes used in toothpastes for sensitive teeth.

One popular brand includes 10% total strontium chloride hexahydrate by weight. Strontium oxide is sometimes used to improve the quality of some pottery glazes. Strontium is also commonly used in aerosol paint, such as the Spanish Montana (Montana Hardcore). This is one of the most likely sources of exposure to the public. Strontium ranelate is used in the treatment of osteoporosis History The mineral strontianite is named after the Scottish village of Strontian, having been discovered in the lead mines there in 1787. [3] Adair Crawford recognized it as differing from other barium minerals in 1790. Strontium itself was discovered in 1798 by Thomas Charles Hope, and metallic strontium was first isolated by Sir Humphry Davy in 1808 using electrolysis . Strontium was among the radioactive materials released by the 1957 Windscale fire. Occurrence In 2005, China was the top producer of strontium with almost two-thirds world share followed by Spain and Mexico, reports the British Geological Survey.

Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development. The metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride : Sr2+ + 2 e- → Sr 2 Cl- → Cl2 ( g ) + 2 e- Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. The largest commercially exploited deposits are found in England.

Main article: Isotopes of strontium The alkali earth metal strontium has four stable, naturally occurring isotopes : 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic ; it is produced by decay from the radioactive alkali metal 87 Rb , which has a half-life of 4.88 × 1010 years. Thus, there are two sources of 87Sr in any material: that formed during primordial nucleo-synthesis along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium , it readily substitutes for Ca in minerals . Sixteen unstable isotopes are known to exist.

Of greatest importance is 90Sr with a half-life of 28.78 years. It is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc, where a lightweight, long-lived, nuclear-electric power source is required. The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. Precautions In its pure form strontium is extremely reactive with air and spontaneously combusts. It is therefore considered to be a fire hazard. Effect on the human body The human body absorbs strontium as if it were calcium . Due to the elements being sufficiently similar chemically, the stable forms of strontium do not pose a significant health threat, but the radioactive 90Sr can lead to various bone disorders and diseases, including bone cancer. The strontium unit is used in measuring radioactivity from absorbed 90Sr.

An innovative drug made by combining strontium with ranelic acid has aided in bone growth, boosted bone density and lessened vertebral, peripheral and hip fractures. [4] [5] Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass. It means that strontium ranelate creates new and strong bone. Strontium ranelate (marketed under the trade names Protelos, Osseor, Protos, Bivalos, Protaxos, Ossum) is registered for treatment of osteoporosis in many countries all over the world. Strontium ranelate has been shown to strengthen bones, according presentations given the IOF World Congress on Osteoporosis, in June of 2006. It also reduced bone resorbtion. Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide.

It needs to be prescribed by a doctor, delivered by a pharmacist and requires a strict medical supervision. Currently, (early 2007) it is not available in Canada or the United States. Several other salts of strontium such as strontium citrate or strontium carbonate are often presented as natural therapies and sold at a dose that is several hundred times higher than the usual strontium intake. Despite the lack of strontium deficit referenced in the medical literature and the lack of information about possible toxicity of strontium supplementation, such compounds can still be sold in the United States under the Dietary Supplements Health and Education Act of 1994. However, their long-term safety and efficacy have never been evaluated on humans using large-scale medical trials. Such compounds should not be administered to humans before further studies are conducted. Allegedly, an attempt was made in 1968 to poison Alexander Dubček with Sr-90, but it failed.

See also Strontium - wikidoc Strontium Sr is stable with 46 neutrons 85Sr Sr is stable with 48 neutrons 87Sr Sr is stable with 49 neutrons 88Sr Sr is stable with 50 neutrons 89Sr References Strontium ( pronounced /ˈstrɒntiəm/) is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal , strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite . The 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years. Contents 10 References Notable characteristics Due to its extreme reactivity to air, this element occurs naturally only in compounds with other elements, as in the minerals strontianite and celestite . Strontium is a bright silvery metal that is softer than calcium and even more reactive in water , which strontium decomposes on contact with to produce strontium hydroxide and hydrogen gas.

It burns in air to produce both strontium oxide and strontium nitride , but since it does not react with nitrogen below 380°C it will only form the oxide spontaneously at room temperature. It should be kept under kerosene to prevent oxidation ; freshly exposed strontium metal rapidly turns a yellowish color with the formation of the oxide. Finely powered strontium metal will ignite spontaneously in air. Volatile strontium salts impart a crimson color to flames , and these salts are used in pyrotechnics and in the production of flares . Natural strontium is a mixture of four stable isotopes . Applications As a pure metal strontium is being used in strontium 90%-aluminium 10% alloys of an eutectic composition for the modification of aluminium-silicon casting alloys. The primary use for strontium compounds is in glass for colour television cathode ray tubes to prevent X-ray emission. Other uses: 89Sr is the active ingredient in Metastron, a radiopharmaceutical used for bone pain secondary to metastatic prostate cancer . The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis .

This localization focuses the radiation exposure on the cancerous lesion. 90Sr has been used as a power source for radioisotope thermoelectric generators (RTGs). 90Sr produces about 0.93 watts of heat per gram (it is lower for the grade of 90Sr used in RTGs, which is strontium fluoride ). [2] However, 90Sr has a lifetime approximately 3 times shorter and has a lower density than 238Pu , another RTG fuel. The main advantage of 90Sr is that it is cheaper than 238Pu and is found in nuclear waste . 90Sr is also used in cancer therapy. Its beta emission and long half-life is ideal for superficial radiotherapy . Strontium is one of the constituents of AJ62 alloy, a durable magnesium alloy used in car and motorcycle engines by BMW . 87Sr/86Sr ratios are commonly used to determine the likely provenance areas of sediment in natural systems, especially in marine and fluvial environments.

Dasch (1969) showed that surface sediments of the deep Atlantic displayed 87Sr/86Sr ratios that could be regarded as bulk averages of the 87Sr/86Sr ratios of geological terranes from adjacent landmasses. One good example of a fluvial system to which Sr isotope ratio studies have been frequently employed is the River Nile (Krom et al, 1999; Krom et al, 2002; Talbot et al. 2000). Due to the vastly differing ages of the rocks that constitute the majority of the Blue and White Nile catchment areas the changing provenance of sediment reaching the River Nile delta, and East Mediterranean Sea beyond, can be discerned through Sr isotopic studies. This information is useful as it can elicit information regarding climate change over geologic time scales. More recently, 87Sr/86Sr ratios have also been used to determine the source of ancient archaeological materials such as timbers and corn in Chaco Canyon, New Mexico (English et al, 2001, Benson et al, 2003).

87Sr/86Sr ratios in teeth may also be used to track animal migrations (Porder et al., 2003) or in criminal forensics. Compounds Strontium carbonate , Strontium nitrate , and Strontium sulfate are commonly used in fireworks for red color. Strontium aluminate is used as a bright phosphor with long persistence of phosphorescence . Strontium chloride is sometimes used in toothpastes for sensitive teeth. One popular brand includes 10% total strontium chloride hexahydrate by weight. Strontium oxide is sometimes used to improve the quality of some pottery glazes . Strontium is also commonly used in aerosol paint, such as the Spanish Montana (Montana Hardcore). This is one of the most likely sources of exposure to the public. Strontium ranelate is used in the treatment of osteoporosis History The mineral strontianite is named after the Scottish village of Strontian , having been discovered in the lead mines there in 1787 . [3] Adair Crawford recognized it as differing from other barium minerals in 1790 .

Strontium itself was discovered in 1798 by Thomas Charles Hope , and metallic strontium was first isolated by Sir Humphry Davy in 1808 using electrolysis . Strontium was among the radioactive materials released by the 1957 Windscale fire . Occurrence File:2005strontium.PNG Strontium output in 2005 In 2005, China was the top producer of strontium with almost two-thirds world share followed by Spain and Mexico, reports the British Geological Survey . Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development.

The metal can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride : Sr2+ + 2 e- → Sr 2 Cl- → Cl2 ( g ) + 2 e- Alternatively it is made by reducing strontium oxide with aluminium in a vacuum at a temperature at which strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. The largest commercially exploited deposits are found in England . Main article: Isotopes of strontium The alkali earth metal strontium has four stable, naturally occurring isotopes : 84Sr (0.56%), 86Sr (9.86%), 87Sr (7.0%) and 88Sr (82.58%). Only 87Sr is radiogenic ; it is produced by decay from the radioactive alkali metal 87 Rb , which has a half-life of 4.88 × 1010 years.

Thus, there are two sources of 87Sr in any material: that formed during primordial nucleo-synthesis along with 84Sr, 86Sr and 88Sr, as well as that formed by radioactive decay of 87Rb. The ratio 87Sr/86Sr is the parameter typically reported in geologic investigations; ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Because strontium has an atomic radius similar to that of calcium , it readily substitutes for Ca in minerals . Sixteen unstable isotopes are known to exist. Of greatest importance is 90Sr with a half-life of 28.78 years. It is a by-product of nuclear fission which is found in nuclear fallout and presents a health problem since it substitutes for calcium in bone , preventing expulsion from the body. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP ( Systems for Nuclear Auxiliary Power ) devices. These devices hold promise for use in spacecraft , remote weather stations, navigational buoys, etc, where a lightweight, long-lived, nuclear-electric power source is required.

The 1986 Chernobyl nuclear accident contaminated a vast area with 90Sr. Precautions In its pure form strontium is extremely reactive with air and spontaneously combusts. It is therefore considered to be a fire hazard . Effect on the human body The human body absorbs strontium as if it were calcium . Due to the elements being sufficiently similar chemically, the stable forms of strontium do not pose a significant health threat, but the radioactive 90Sr can lead to various bone disorders and diseases , including bone cancer . The strontium unit is used in measuring radioactivity from absorbed 90Sr. An innovative drug made by combining strontium with ranelic acid has aided in bone growth, boosted bone density and lessened vertebral, peripheral and hip fractures . [4] [5] Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass.

It means that strontium ranelate creates new and strong bone. Strontium ranelate (marketed under the trade names Protelos, Osseor, Protos, Bivalos, Protaxos, Ossum) is registered for treatment of osteoporosis in many countries all over the world. Strontium ranelate has been shown to strengthen bones, according presentations given the IOF World Congress on Osteoporosis, in June of 2006. It also reduced bone resorbtion. Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It needs to be prescribed by a doctor, delivered by a pharmacist and requires a strict medical supervision. Currently, (early 2007) it is not available in Canada or the United States. Several other salts of strontium such as strontium citrate or strontium carbonate are often presented as natural therapies and sold at a dose that is several hundred times higher than the usual strontium intake.

Despite the lack of strontium deficit referenced in the medical literature and the lack of information about possible toxicity of strontium supplementation, such compounds can still be sold in the United States under the Dietary Supplements Health and Education Act of 1994. However, their long-term safety and efficacy have never been evaluated on humans using large-scale medical trials. Such compounds should not be administered to humans before further studies are conducted. Allegedly, an attempt was made in 1968 to poison Alexander Dubček with Sr-90, but it failed. See also

Question: Named after a Scottish village near where it was discovered in 1790, what soft metal element, symbol Sr, was used to make cathode ray TV tubes?
Answer: Strontium