Boron is a metalloid and was discovered by Joseph L. Gay-Lussac and L. J. Thénard in 1808. It is chemically unreactive and is the second hardest element on earth.
History and Discovery
Boron is an ancient metal and have been known to human civilization since thousands of years. Its compound, sodium tetraborate that is commonly known as borax have been used in the manufacturing of glass in very early time. Boron was discovered by Joseph L. Gay-Lussac and L. J. Thénard in 1808 that was around 60% pure. The pure form of boron was isolate by Henri Moissan (French chemist) in 1892 and then in 1909, almost 100% pure boron was isolated by Ezekiel Weintraub. The name borax has been originated from buraq (Arabic) and burah (Persian) meaning “white” [1].
Boron
| Periodic Table Classification | Group 13 Period 2 |
|---|---|
| State at 20C | Solid |
| Color | Black-brown |
| Electron Configuration | [He] 2s2 2p1 |
| Electron Number | 5 |
| Proton Number | 5 |
| Electron Shell | 2, 3 |
| Density | 2.34 g.cm-3 at 20°C |
| Atomic number | 5 |
| Atomic Mass | 10.81 g.mol -1 |
| Electronegativity according to Pauling | 2.04 |
Occurrence
Boron has an average abundance on Earth and is present in a concentration of 10 ppm in the Earth’s crust. In nature, boron does not exist in free or elemental form but in the form of compounds. Boron is present embedded in sedimentary rocks and sediments. It is also present in volcanic spring waters. The primary sources of boron are borax ore ((Na 2 B 4 O 7), kernite (Na2B4O6(OH)2.3H2O) and colemanite (CaB3O4(OH)4.H2O). These ores or minerals are present in desert areas. The largest producers of boron are USA and Turkey [2].
Physical Characteristics
Boron is a hard metal and is considered the second hardest element in the world. Boron has a unique nature, as it has characteristics that are intermediate between non-metals and metals and thus considered as a metalloid. Boron is quite distinct element in its group, as all other members of Group 13 are true metals. Boron exists in various allotropic forms (different forms of same elements that have different chemical and physical properties). Due to these allotropic forms, boron can exist as red crystals, black crystals or brown powder. Boron, in all allotropic forms have a high boiling point. Boron is a heat resistant element. It has one of the highest boiling points. Boron can absorb neutrons with great efficiency. At room temperature, boron is an insulator, but its electrical conductivity increases with an increase in temperature [3].
Chemical Characteristics
Amorphous form of boron is reactive. In crystalline form, boron is quite unreactive. It makes stable covalent bonds with other compounds and does not forms ionic bonds. Boron combines with air to form boron trioxide, which acts a protective layer on the surface of boron and protects the metal from further oxidation. Born in powdered form reacts with hot sulfuric acid and nitric acid and dissolves in molten metals [4].
Significance and Uses
- Boron is widely used in the making of glass, glass fiber, borosilicate fiber and ceramic products.
- Boric acid is used as an antiseptic to treat mild infections.
- Boron is also compound of fertilizers.
- Boron is used in the manufacturing of various alloys to impart desirable characteristics. For instance, the strongest magnets are made from alloys of boron with iron and neodymium. Various electronic devices use these magnets, such as headphones, loudspeakers and particle accelerators.
- Boron coating and alloys are widely used a flame retardant (material that prevent burning of other material).
- Boron is used as doping agent in making silicon semiconductors used in electronic devices.
- It is also used an active component of herbicides and insecticides.
- Boron is a major component of ceramic equipment used for carrying out high-temperatures tasks.
- Boron is used in making bullet proof vests, vehicles and armor trucks.
- Boron nitride and boron carbide as used in making refractory materials such as oven, incinerators.
Health Hazards
Boron is non-toxic. Boron plays various roles in the bodies of plants and animals as micronutrient. In plants, boron plays important role in regulation of certain proteins and it aids the plants in uptake of water from soil. Boron deficiency can lead to crumpled and twisted leaves in plants. In animals, boron deficiency can lead to bone defects as boron plays important role in maintain healthy bones. The daily recommended dose of boron in humans in around 3 milligrams. Various nuts, beans, green vegetables and fruits help fulfill the required boron need of the body [5].
Isotopes of Boron
Boron has eleven isotopes, with mass number ranging from seven to seventeen. There are two isotopes in naturally occurring boron, boron-10 and boron-11. Boron-10 is widely used in nuclear reactors for capturing and absorbing of neutrons.
REFERENCES
[1]. Alaa S. Abd-El-Aziz, Macromolecules Containing Metal and Metal-Like Elements Volume 8 Boron-Containing Polymers., (2007) p2. Wiley-Interscience
[2]. “U.S. Borax Boron Mine”. The Center for Land Use Interpretation, Ludb.clui.org. Retrieved 2013-04-26.
[3]. http://www.chemistryexplained.com/elements/A-C/Boron.html
[4] Laubengayer, A. W.; Hurd, D. T.; Newkirk, A. E.; Hoard, J. L. (1943). “Boron. I. Preparation and Properties of Pure Crystalline Boron”. Journal of the American Chemical Society. 65 (10): 1924–1931. doi:10.1021/ja01250a036.
[5]. Pizzorno, L (Aug 2015). “Nothing boring about boron”. Integrative Medicine. 14 (4): 35&ndash, 48. PMC 4712861. PMID 26770156.