Strontium

Calcium (Fluoro, Chloro, Hydroxyl) Phosphate
Ca₅(PO₄)₃(OH,F,Cl)

Strontium is kept under kerosene to prevent oxidation.

The History Says

Metallic strontium was first isolated in 1808 by Sir Humphry Davy using electrolysis. Before him, Hope discovered it in the year 1798. It is named such for the village of Strontian in Scotland. However, Scottish scientist Adair Crawford discovered a new mineral in 1790 known as strontianite.

The Present Scenario

Since 1959, Strontium minerals have not been mined in the USA. Hence, the US companies import all its need of the strontium minerals. Mostly they are exported from Mexico.

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Strontium is an alkaline earth metal of soft silver-white or yellowish metallic element which is highly reactive, chemically. It always occur naturally, as it is extremely reactive to air, combined with other elements and compounds, like minerals strontianite, celestite, etc. It is isolated as a yellowish metal and is to some extent malleable.

It is softer than calcium and is more reactive in water. In contact with water, it decomposes to produce strontium hydroxide and hydrogen gas. In air it burns and produces strontium oxide and strontium nitride, but as it does not react with nitrogen below 380°C, it will only form the oxide spontaneously at room temperature.

Strontium are kept under kerosene to prevent it from oxidation. Freshly exposed strontium metal turns yellowish forming oxide and finely powdered strontium metal ignites spontaneously in air.

Volatile strontium salts become crimson color to flames, and are used in pyrotechnics and in the production of flares.

Physical Properties of Strontium

Phase	Solid
Density (near room temperature)	2.64 g/cm3
Liquid addition at melting point	6.980 g/cm3
Melting point	1050 K (777°C, 1431°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 of Strontium

Crystal structure	Cubic face centered
Oxidation states	2 (strongly basic oxide)
Electronegativity	0.95 (Pauling scale)
Ionization energies	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

Applications of Strontium

The primary use of Strontium presently is in glass for color television cathode ray tubes. It is also used for some other commercial purposes. They are as follows:

• For the production of ferrite magnets and refining zinc.
• For a variety of optics applications as it has extremely high refractive index and an optical dispersion which are greater than diamond.
• Strontium titanate is cut into gemstones and is used as diamond simulant, but it is very soft and scratches easily.
• In fireworks for red color.
• Strontium aluminate as bright phosphor with long persistence of phosphrescence.
• Strontium chloride, not often, used in toothpastes for sensitive teeth.
• Strontium-89 is an active ingrdient in Metastron, a radiopharmaceutical, which is used for bone pain secondary to metastatic prostate cancer.
• Strontium-90 is used as a power source for Radioisotope thermoelectric generator (RTGs). It produces about 0.46 watts of heat per gram, i.e. 15% less power per gram then plutonium-238, the most common RTG fuel. It also decays approximately 3 times quicker than plutonium-238.
• Strontium-90 is also used in cancer therapy. The beta emission of strontium-90 and long half-life is ideal for superficial radio-therapy.

Effect of Strontium on the Human Body

The stable form of strontium is not a threat to the health of human body, but the radioactive strontium-90 leads to various bone disorders and diseases, even to the extent of bone cancer. Strontium units are used in measuring radioactivity from the absorbed strontium-90.

Kindly note that the human body absorbs strontium as if it were calcium. This is due to the sufficient chemical similarities in both the elements.