Antimony
For some time, China has been the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods to produce antimony are roasting and subsequent carbothermal reduction or direct reduction of stibnite with iron.
The largest applications for metallic antimony are as alloying material for lead and tin and for lead antimony plates in lead-acid batteries. Alloying lead and tin with antimony improves the properties of the alloys which are used in solders, bullets and plain bearings. Antimony compounds are prominent additives for chlorine- and bromine-containing fire retardants found in many commercial and domestic products. An emerging application is the use of antimony in microelectronics.
Occurrence
The abundance of antimony in the Earth's crust is estimated at 0.2 to 0.5 parts per million, comparable to thallium at 0.5 parts per million and silver at 0.07 ppm. Even though this element is not abundant, it is found in over 100 mineral species. Antimony is sometimes found natively, but more frequently it is found in the sulfide stibnite (Sb2S3) which is the predominant ore mineral.
| Symbol | Sb | |
| Atomic Number | 51 | |
| Atomic Weight | 121.757 | |
| Oxidation States | +3,+5,-3 | |
| Electronegativity, Pauling | 2.05 | |
| State at RT | Solid, Metalloid | |
| Melting Point, K | 903.9 | |
| Boiling Point, K | 1908 |
Appearance and Characteristics
Harmful effects:
Like arsenic, which sits directly above it in the periodic table, the toxicity of antimony and its compounds varies according to the chemical state of the element. Many of the salts are carcinogenic.
The metallic form is considered to be less active whereas stibine (SbH3) and stibnite (Sb2S3) are extremely toxic. Antimony is toxic and immediately dangerous to life or health at 50 mg m-3 or above.
Exposure to 9 milligrams per cubic meter of air (mg/m3) of antimony as stibnite for a long time can irritate your eyes, skin, and lungs. Breathing 2 mg/m3 of antimony for a long time can cause problems with the lungs (pneumoconiosis) heart problems (altered electrocardiograms), stomach pain, diarrhea, vomiting and stomach ulcers. People who drank over 19 ppm of antimony in one sitting vomited.
Characteristics:
- Antimony is metalloid, so it has some metallic properties but not enough to be classified as a true metal. Physically, it behaves like sulfur while chemically it is more metallic.
- Antimony’s electrical and thermal conductivity are lower than most metals’ conductivities.
- Antimony is a brittle, fusible, crystalline solid. It is easily powdered.
- Antimony also has the unusual property that (like water) it expands as it freezes. Four other elements expand when they freeze; silicon, bismuth, gallium and germanium.
- In addition to the usual form of antimony, there are three allotropes: yellow crystalline, amorphous black, and explosive.
Uses of Antimony
- The major use of antimony is in lead alloys – mainly for use in batteries – adding hardness and smoothness of finish. The higher the proportion of antimony in the alloy, the harder and more brittle it will be. Alloys made with antimony expand on cooling, retaining the finer details of molds. Antimony alloys are therefore used in making typefaces for clear, sharp printing.
- Babbit metals, used for machinery bearings, are alloys of lead, tin, copper and antimony. These metals are hard but slippery and so ideal for use as bearings.
- Antimony is used in the semiconductor industry as an n-type dopant for silicon.
- Antimony trioxide is used as a flame retardant in adhesives, plastics, rubber and textiles.
Antimony was used as a catalyst in CFC production.
Rotating 3D molecular model of antimony pentachloride.
