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Strontium (pronounced /ˈstrɒnʃiəm/, /ˈstrɒntiəm/, or /ˈstrɒnʃəm/) 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 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.

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. 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 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 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 one of the constituents of AJ62 alloy, a durable magnesium alloy used in car and motorcycle engines by BMW.
Since Strontium is so similar to calcium, it is incorporated in the bone. All four 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.
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.
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 (Krom et al., 1999; Krom et al., 2002; Talbot et al. 2000). 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 (English et al., 2001; Benson et al., 2003). 87Sr/86Sr ratios in teeth may also be used to track animal migrations (Barnett-Johnson, 2007; Porder et al., 2003) or in criminal forensics.

Strontium atoms are used in an experimental atomic clock with record-setting accuracy

一种金属元素，银白色结晶，它的化合物燃烧时发出红色火焰，用来制造焰火等，亦可入药。
元素名称：锶
　　原子化焓：kJ /mol @25℃
　　163.2
　　热容：J /（mol· K）
　　26.4
　　导电性：10^6/(cm ·Ω )
　　0.0762
　　元素在宇宙中的含量:(ppm)
　　0.04
　　导热系数：W/（m·K）
　　35.4
　　熔化热:(千焦/摩尔)
　　8.30
　　汽化热:(千焦/摩尔)
　　144.0
　　原子体积:(立方厘米/摩尔)
　　33.7
　　元素符号：Sr
　　元素英文名称：
　　元素类型：金属元素
　　元素在太阳中的含量:(ppm) (ppm是浓度单位,1ppm表示1单位溶剂中含有百万分之一单位的溶质)
　　0.05
　　元素在海水中的含量:(ppm)
　　太平洋表面 7.6
　　地壳中含量：（ppm）
　　370
　　相对原子质量：87.62
　　原子序数：38
　　质子数：38
　　中子数：50
　　同位素:Sr-84 Sr-86 Sr-87 Sr-88(放射)
　　摩尔质量：88
　　原子半径：2.45
　　所属周期：5
　　所属族数：IIA
　　电子层排布： 2-8-18-8-2
　　氧化态：
　　Main Sr+2
　　Other
　　晶胞为面心立方晶胞，每个晶胞含有4个金属原子。
　　晶胞参数：
　　a = 608.49 pm
　　b = 608.49 pm
　　c = 608.49 pm
　　α = 90°
　　β = 90°
　　γ = 90°
　　莫氏硬度：1.5
　　电离能 (kJ /mol)
　　M - M+ 549.5
　　M+ - M2+ 1064.2
　　M2+ - M3+ 4210
　　M3+ - M4+ 5500
　　M4+ - M5+ 6910
　　M5+ - M6+ 8760
　　M6+ - M7+ 10200
　　M7+ - M8+ 11800
　　M8+ - M9+ 15600
　　M9+ - M10+ 17100
　　常见化合价：+2
　　单质：锶
　　单质化学符号：Sr
　　颜色和状态：
　　密度： 2.6
　　熔点： 769
　　沸点： 1384
　　发现人：克劳福特、戴维 发现年代：1808年
　　发现过程：
　　1808年，英国的克劳福特和戴维先后由铅矿和锶矿中发现了锶。
　　元素描述：
　　银白色软金属。密度2.6克/厘米3。熔点769℃。沸点1384℃。化合价+2。第一电离能5.695电子伏特。化学性质活泼，于空气中加热时能燃烧；易与水和酸作用而放出氢；在到熔点时即燃烧而呈洋红色火焰。
　　元素来源：
　　锶是碱土金属中丰度最小的元素。主要的矿物有天青石和碳酸锶矿。可由电解熔融的氯化锶而制得。
　　元素用途：
　　用于制造合金、光电管，以及分析化学、烟火等。质量数90的锶是一种放射性同位素，可作β射线放射源，半衰期为25年。
　　元素辅助资料：
　　钡、锶、钙和镁同是碱土金属，也是地壳中含量较多的元素。不过钡和锶在地壳中的含量与钙、镁相比，还是较少的。再加上它们的化合物的实际应用不及钙和镁的化合物广泛。因此它们的化合物比钙和镁的化合物晚些被人们认识，只是戴维把钡和锶和钙、镁同时从化合物中电解分离出来。
　　大约在1787年间，在欧洲一些展览会上展出从英国苏格兰思特朗蒂安（strontian）地方的铅矿中采得的一种矿石。一些化学家认为它是一种萤石。大约在1791到1792年间，英国化学家、医生荷普研究了这种矿石，明确它是碳酸盐，但是与碳酸钡不同，肯定其中含有一种新土，就从它的产地Strontian命名它为strontia（锶土）。1789年拉瓦锡发表的元素表中就没有来得及把锶土排进去。而戴维却赶上了，他在1808年利用电解法，从碳酸锶中分离出金属锶，就命名为 strontium，元素符号用Sr。