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.
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.
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