Difference between revisions of "Strontium" - New World Encyclopedia

Vapor pressure
38	rubidium ← strontium → yttrium
	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/cm³
Liquid density at m.p.	6.980 g/cm³
Melting point	1050 K; (777 °C, 1431 °F)
Boiling point	1655 K; (1382 °C, 2520 °F)
Heat of fusion	7.43 kJ/mol
Heat of vaporization	136.9 kJ/mol
Heat capacity	(25 °C) 26.4 J/(mol·K)
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
	2nd: 1064.2 kJ/mol
	3rd: 4138 kJ/mol
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·K)
Thermal expansion	(25 °C) 22.5 µm/(m·K)
Shear modulus	6.1 GPa
Poisson ratio	0.28
Mohs hardness	1.5
CAS registry number	7440-24-6
Notable isotopes

Revision as of 14:59, 6 October 2006

Strontium (chemical symbol Sr, atomic number 38) is a soft, silvery 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.

is a chemical element in the periodic table that has the.

An alkaline earth metal, strontium

The ⁹⁰Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.

Occurrence and isolation

Strontium occurs commonly in nature amd has been estimated to be the fifteenth most abundant element on Earth, averaging 0.034% of all igneous rock. Given its extreme reactivity, its natural occurrence is only in the form of compounds with other elements. Its chief minerals are celestite (strontium sulfate, SrS O₄) and strontianite (strontium carbonate, SrCO₃). The largest commercially exploited deposits are found in England.

Of the two minerals, celestite occurs in sufficient amounts in sedimentary deposits to make development of mining facilities attractive. It would be more useful to mine strontianite because strontium is used more often in the carbonate form, but there are relatively few known deposits suitable for development.

The metallic form of strontium can be prepared by electrolysis of melted strontium chloride mixed with potassium chloride. The reactions at the electrodes can be represented as follows.

cathode: Sr²⁺ + 2 e^- → Sr

anode: 2 Cl^- → Cl_{2 (g)} + 2 e^-

Alternatively, strontium can be produced by reducing strontium oxide with aluminum in a vacuum, at a temperature at which strontium distills off.

History

In 1790, while examining samples of the barium mineral witherite (barium carbonate, BaCO3), Adair Crawford found the samples to contain a previously unrecorded mineral. The new mineral was named strontianite, after the Scottish village of Strontian. The element strontium itself was discovered in 1798, and metallic strontium was first isolated by Sir Humphry Davy in 1808, by the method of electrolysis.

Strontium was among the radioactive materials released during a fire at a British nuclear reactor at Windscale, Cumbria, in 1957.

Notable characteristics

As a member of the series of alkaline earth metals, strontium lies in group 2 (former group 2A) of the periodic table, between calcium and barium. In addition, it is placed in period 5, between rubidium and yttrium. As its atomic radius is similar to that of calcium, it readily substitutes for calcium in minerals.

Freshly prepared strontium has a bright silvery color, but on exposure to air it forms the yellow oxide.

It is softer than calcium and even more reactive in water. On contact with water, strontium reacts 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;

Finely powdered strontium metal will ignite spontaneously in air. Volatile strontium salts impart a beautiful crimson color to flames, and these salts are used in pyrotechnics and in the production of flares.

Three allotropes of the metal exist, with transition points at 235 and 540 °C.

Natural strontium is a mixture of four stable isotopes.

Isotopes

In nature, strontium occurs as four stable isotopes: ⁸⁴Sr (0.56%), ⁸⁶Sr (9.86%), ⁸⁷Sr (7.0%), and ⁸⁸Sr (82.58%). Of these, 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 during primordial nucleosynthesis 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.

In addition to the stable isotopes, 16 unstable isotopes of strontium are known. Of greatest importance is ⁹⁰Sr, with a half-life of 28.78 years. It is a byproduct 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.

Applications

Commercial uses of strontium and its compounds:

Strontium is widely used in the screen glass (cathode ray tubes) of color television sets.
It is commonly used in pyrotechnic displays, for its ability to produce a red color.
Aerosol paints may contain strontium. This appears to be one of the most likely sources of public exposure to strontium.
Strontium is used for the production of ferrite magnets and refining zinc.
Strontium titanate has an extremely high refractive index and optical dispersion, making it useful in a variety of applications in optics. It can act as a diamond simulant, but it is rarely used for that purpose because of its extreme softness and vulnerability to scratching.
Strontium aluminate is used as a bright phosphor, with long persistence of phosphorescence.
Strontium chloride is occasionally used in toothpastes for sensitive teeth.
Strontium oxide is sometimes used to improve the quality of pottery glazes.
⁹⁰Sr has been used as a power source for radioisotope thermoelectric generators (RTGs), which are simple electrical generators that obtain their power from the heat produced by the decay of radioactive elements.[1]

Medical uses

The isotope ⁸⁹Sr is the active ingredient in Metastron, a radioactive pharmaceutical used for bone pain accompanying metastatic prostate cancer. The strontium acts like calcium and is preferentially incorporated into bone at sites of increased osteogenesis (bone development). This localization focuses the radiation exposure on the cancerous lesion.

The radioisotope ⁹⁰Sr is also used in cancer therapy. Its beta emission and long half-life are ideal for superficial radiotherapy.

An experimental drug made by combining strontium with ranelic acid has aided in bone growth, boosted bone density, and lessened fractures (El-Hajj, 2004; Meunier et al., 2004). Strontium ranelate is registered in Europe for the treatment of osteoporosis.

Precautions

Pure strontium is extremely reactive with air and burns spontaneously. It is therefore considered a fire hazard.

Effects on the human body

The human body absorbs strontium as if it were calcium. These two elements are chemically so similar that the stable forms of strontium do not pose a significant health threat. By contrast, the radioactive isotope ⁹⁰Sr can lead to various bone disorders and diseases, including bone cancer. The "strontium unit" is used in measuring radioactivity from absorbed ⁹⁰Sr.

References
ISBN links support NWE through referral fees

Los Alamos National Laboratory – Strontium. Retrieved October 6, 2006.
El-Hajj Fuleihan G. (2004). Strontium ranelate — a novel therapy for osteoporosis or a permutation of the same?. New England Journal of Medicine 350 (Jan 29): 504-506. PMID 14749460.
Meunier PJ, Roux C, Seeman E, Ortolani S, Badurski JE, Spector TD, Cannata J, Balogh A, Lemmel EM, Pors-Nielsen S, Rizzoli R, Genant HK, Reginster JY (2004). The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis. New England Journal of Medicine 350 (Jan 29): 459-468. PMID 14749454.

External links

WebElements.com – Strontium

Credits

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@@ Line 70: / Line 70: @@
 == Occurrence and isolation ==
-Strontium occurs commonly in nature amd has been estimated to be the fifteenth most abundant element on [[Earth]], averaging 0.034% of all igneous rock. It is found chiefly in the form of minerals [[celestite]]* (strontium sulfate, Sr[[sulfur|S]][[oxygen|O]]<sub>4</sub>) and [[strontianite]]* (strontium carbonate, Sr[[carbon|C]]O<sub>3</sub>). The largest commercially exploited deposits are found in [[England]].
+Strontium occurs commonly in nature amd has been estimated to be the fifteenth most abundant element on [[Earth]], averaging 0.034% of all igneous rock. Given its extreme reactivity, its natural occurrence is only in the form of compounds with other elements. Its chief minerals are [[celestite]]* (strontium sulfate, Sr[[sulfur|S]][[oxygen|O]]<sub>4</sub>) and [[strontianite]]* (strontium carbonate, Sr[[carbon|C]]O<sub>3</sub>). The largest commercially exploited deposits are found in [[England]].
 Of the two minerals, celestite occurs in sufficient amounts in sedimentary deposits to make development of mining facilities attractive. It would be more useful to mine strontianite because strontium is used more often in the carbonate form, but there are relatively few known deposits suitable for development.
@@ Line 89: / Line 89: @@
 == Notable characteristics ==
-Given its extreme reactivity to air, this element occurs naturally only in compounds with other elements, as in the minerals strontianite, celestite, etc. It is isolated as a yellowish metal and is somewhat malleable. It is chiefly employed (as strontium nitrate) to add red color to pyrotechnic flames.
+As a member of the series of [[alkaline earth metal]]s, strontium lies in group 2 (former group 2A) of the periodic table, between calcium and barium. In addition, it is placed in period 5, between rubidium and yttrium. As its [[atomic radius]]* is similar to that of [[calcium]], it readily substitutes for calcium in [[mineral]]s.
-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 [[yellow|yellowish]] color with the formation of the oxide. Finely powdered strontium metal will ignite spontaneously in air. Volatile strontium salts impart a beautiful [[red|crimson]] color to [[fire|flames]], and these salts are used in [[pyrotechnic]]s and in the production of [[flare (pyrotechnic)|flares]].
+Freshly prepared strontium has a bright silvery color, but on exposure to air it forms the yellow oxide.
+It is softer than [[calcium]] and even more reactive in [[water]]. On contact with water, strontium reacts 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]];
+Finely powdered strontium metal will ignite spontaneously in air. Volatile strontium salts impart a beautiful [[red|crimson]] color to [[fire|flames]], and these salts are used in [[pyrotechnic]]s and in the production of [[flare (pyrotechnic)|flares]].
 * Three [[allotropes]] of the metal exist, with [[transition point]]s at 235 and 540 °C.
@@ Line 97: / Line 105: @@
 * Natural strontium is a mixture of four stable [[isotope]]s.
-* Because strontium has an [[atomic radius]] similar to that of [[calcium]], it readily substitutes for Ca in [[mineral]]s.
 === Isotopes ===
@@ Line 106: / Line 114: @@
 == Applications ==
-At present the primary use for strontium is in [[glass]] for [[color]] television [[cathode ray tube]]s.
-Other commercial uses:
-*Production of [[ferrite magnet]]s and refining [[zinc]].
+Commercial uses of strontium and its compounds:
-*[[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 is widely used in the screen [[glass]] ([[cathode ray tube]]*s) of color [[television]] sets.
-*Strontium titanate has been cut into [[gemstone]]s, in particular for its use as [[diamond simulant]]. However, it is very soft and easily scratches so it is rarely used.
+*It is commonly used in [[pyrotechnic]] displays, for its ability to produce a red color.
-*Strontium is also used in [[firework]]s for red color, it's sometimes used in the [[theatre]], film and [[television industry]] for [[pyrotechnic]] [[special effects]].
+*Aerosol paints may contain strontium. This appears to be one of the most likely sources of public exposure to strontium.
-*[[Strontium aluminate]] is used as a bright [[phosphor]] with long persistence of [[phosphorescence]].
+*Strontium is used for the production of [[ferrite magnet]]*s and refining [[zinc]].
-*[[Strontium chloride]] is sometimes used in [[toothpaste]]s for sensitive teeth.  One popular brand includes 10% strontium chloride hexahydrate by weight.
+*[[Strontium titanate]]* has an extremely high [[refractive index]]* and [[optical dispersion]]*, making it useful in a variety of applications in optics. It can act as a [[diamond]] simulant, but it is rarely used for that purpose because of its extreme softness and vulnerability to scratching.
-*[[Strontium oxide]] is sometimes used to improve the quality of some [[pottery]] [[glaze#Ceramic glazes|glazes]].
+*[[Strontium aluminate]]* is used as a bright [[phosphor]]*, with long persistence of [[phosphorescence]].
-*[[strontium-89|<sup>89</sup>Sr]] 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.
+*[[Strontium chloride]]* is occasionally used in [[toothpaste]]*s for sensitive teeth.
-*[[strontium-90|<sup>90</sup>Sr]] has been used as a power source for [[Radioisotope thermoelectric generator|RTG]]s. <sup>90</sup>Sr produces about 0.93 watts of heat per gram (it is lower for the grade of <sup>90</sup>Sr used in RTGs, which is [[strontium fluoride]]). [http://www.qrg.northwestern.edu/projects/vss/docs/Power/3-what-are-the-fuels-for-rtgs.html] However, <sup>90</sup>Sr has a lifetime approximately 3 times shorter and has a lower density than [[plutonium-238|<sup>238</sup>Pu]], another [[RTG]] fuel. The main advantage of <sup>90</sup>Sr is that it is cheaper than <sup>238</sup>Pu and is found in [[nuclear waste]].
+*[[Strontium oxide]]* is sometimes used to improve the quality of [[pottery]]* [[glaze#Ceramic glazes|glazes]]*.
-*<sup>90</sup>Sr is also used in [[cancer]] therapy.  Its beta emission and long half-life is ideal for superficial [[radiotherapy]].
+*[[strontium-90|<sup>90</sup>Sr]] has been used as a power source for [[radioisotope thermoelectric generator]]*s (RTGs), which are simple electrical generators that obtain their power from the heat produced by the decay of radioactive elements.[http://www.qrg.northwestern.edu/projects/vss/docs/Power/3-what-are-the-fuels-for-rtgs.html]
-*Strontium is also commonly used in aerosol paint, such as the [[Spanish Montana]] (Montana Hardcore). This is one of the most likely source of exposure to the public.
+=== Medical uses ===
+*The isotope [[strontium-89|<sup>89</sup>Sr]] is the active ingredient in Metastron, a radioactive [[pharmaceutical]] used for bone pain accompanying [[metastatic]]* prostate [[cancer]]. The strontium acts like [[calcium]] and is preferentially incorporated into bone at sites of increased [[osteogenesis]]* (bone development). This localization focuses the radiation exposure on the cancerous lesion.
+*The radioisotope <sup>90</sup>Sr is also used in [[cancer]] therapy. Its beta emission and long half-life are ideal for superficial [[radiotherapy]]*.
+*An experimental drug made by combining strontium with [[ranelic acid]]* has aided in [[bone]] growth, boosted bone density, and lessened [[Fracture (bone)|fracture]]*s (El-Hajj, 2004; Meunier ''et al.'', 2004). Strontium ranelate is registered in Europe for the treatment of osteoporosis.
 == Precautions ==
@@ Line 138: / Line 146: @@
 ==References==
-* {{cite web | title=Los Alamos National Laboratory &ndash; Strontium | url=http://periodic.lanl.gov/elements/38.html | accessdate=August 5 | accessyear=2005 }}
+* {{cite web | title=Los Alamos National Laboratory &ndash; Strontium | url=http://periodic.lanl.gov/elements/38.html | accessdate=October 6 | accessyear=2006 }}
 * {{cite journal | author=El-Hajj Fuleihan G. | title=Strontium ranelate — a novel therapy for osteoporosis or a permutation of the same? | journal=New England Journal of Medicine | volume=350 | issue=Jan 29 | year=2004 |pages=504-506 | id=PMID 14749460}}
 * {{cite journal | author=Meunier PJ, Roux C, Seeman E, Ortolani S, Badurski JE, Spector TD, Cannata J, Balogh A, Lemmel EM, Pors-Nielsen S, Rizzoli R, Genant HK, Reginster JY | title=The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis | journal=New England Journal of Medicine | volume=350 | issue=Jan 29 | year=2004 | pages=459-468 | id=PMID 14749454}}

Difference between revisions of "Strontium" - New World Encyclopedia

Revision as of 14:59, 6 October 2006

Contents

Occurrence and isolation

History

Notable characteristics

Isotopes

Applications

Medical uses

Precautions

Effects on the human body

See also

References
ISBN links support NWE through referral fees

External links

Credits

Difference between revisions of "Strontium" - New World Encyclopedia

Revision as of 14:59, 6 October 2006

Occurrence and isolation

History

Notable characteristics

Isotopes

Applications

Medical uses

Precautions

Effects on the human body

See also

ReferencesISBN links support NWE through referral fees

External links

Credits

References
ISBN links support NWE through referral fees