B
Atomic No. - 5
Boron nitride can be used to make materials that are almost as hard as diamond.
The History Says
Boron minerals, especially borax were traded more than thousand years ago. Then, sheep, camel and yak caravans transportaed borax from desert salt beds in Persia and Tibet to the Arab countries and also to India, mainly for making glass.
The Present Scenario
Boron's effect on animals is under study. Still there is no evidence of boron being necessary for animal health, though a small quantity might stimulate bone and muscle growth. Parallel to it, it is also an important trace element for green algae and higher plants used in agriculture.
BORON, a semi-metallic element, exhibits some properties of metal as well as of non-metal. It is dark, amorphous and unreactive solid in its elemental form. It occurs abundantly in the borax ore. The metallic form of boran is hard and a bad conductor in room temperatures. It is never found free in nature. Crystalline boron exists in many polymorphs. Boron is also similar to carbon because of its capability of forming stable covalent bonded molecular networks.
Boron has a deficiency of electrons and possesses a vacant p-orbital. It is an electrophile, attracted to electrons. Compounds of boron often behave as Lewis acids. It transmits infrared light. It is a poor electrical conductor at standard temperatures. Boron nitride is used to make harder materials. This element also has a lubricating quality like graphite.
The name 'boron' has been derived from the mineral borax. It is thought to have come from the Persian name 'burah,' which meant this particular mineral. The element boron was identified in 1808 by Sir Humphrey Davy of England, and Joseph-Louis Gay-Lussac and Louis Jacques Thenard of France. They discovered that it can be produced by combining boric acid (H3BO3) and metallic potassium.
Physical Properties of Boron
| Phase | Solid |
| Density (near room temperature) | 2.34 g/cm3 |
| Liquid density at melting point | 2.08 g/cm3 |
| Melting point | 2349 K (2076°C, 3769°F) |
| Boiling point | 4200 K (3927°C, 7101°F) |
| Heat of fusion | 50.2 kJ/mol |
| Heat of vaporization | 480 kJ/mol |
| Heat capacity | (25°C) 11.087 J/(mol-K) |
Atomic Properties of Boron
| Crystal structure | Rhombohedral |
| Oxidation states | 3 (mildly acidic oxide) |
| Electronegativity | 2.04 (Pauling scale) |
| Ionization energies | 1st: 800.6 kJ/mol 2nd: 2427.1 kJ/mol 3rd: 3659.7 kJ/mol |
| Atomic radius | 85 pm |
| Atomic radius (calc.) | 87 pm |
| Covalent radius | 82 pm |
Uses of Boron
- Sodium tetraborate pentabydrate (Na2B4O7.5H2O), a compound of boron is used in making insulating fibreglass and sodium perborate bleach.
- Orthoboric acid (H3BO4) or boric acid is used in the production of textile fibreglass and flat panel displays or eye drops.
- Borax (sodium tetraborate decahydrate, Na2B4O7.10H2O) is used in the production of adhesives, anti-corrosion systems and in many other uses.
- Boron is used in agriculture as it plays a notable role in plant fertilisation and in building of cell wall structures.
- It gives distinctive green flame, hence used in pyrotechnic flares.
- Boric acid is used in traditionally as insecticide, especially against ants or cockroaches.
- Compounds of boron are used in synthesis and in the manufacturing process of borosilicate and borophophosilicate glasses. They are also used as wood preservatives.
- Boron-10 assists in the controlling of nuclear reactors, a shield against radiation and in neutron detection.
- Purified boron-11, also known as depleted boron, is used for borosilicate glasses in rad-hard electronics.
- Boron filaments for its high-strength and lightweight property is used in advanced aerospace structures as a component of composite materials.
- Sodium borohydride (NaBH4) is used for reducing aldehydes and ketones to alcohols.
- Boron in trace amount is also used in P-type semiconductors as dopant.
Substitutes and Alternative Sources of Boron
Boron compounds are replaced by chlorine and enzymes in detergents. Making of enamels and glass products, lithium compounds are used. However, the boron ores, which has been known, can easily last meeting the demands for boron compounds for many coming years.
Occurrences of Boron
- United States (especially California)
- Turkey
- Chile
- Argentina
- Iran
- Russia