Boron is a shiny, black semimetal with semiconductor properties. It is a hard but brittle substance and can be found in commercially viable concentrations in minerals such as borax and kernite, and also in other minerals such as ulexite and tourmaline. The chemical behaviour of boron is non-metallic. Boric acid occurs naturally, especially in Italy, as sassolite. The nucleus of the most common boron isotope consists of five protons and six neutrons.
Essential Facts
| Atomic number | 5 |
| Name | Boron |
| Symbol | B |
| Atomic mass | 10.811 |
| Classification | Semimetal |
| State at 20°C | Solid |
| Melting point | 2200°C |
| Boiling point | 2550°C |
History
Boron was isolated in 1808 by heating boron oxide with potassium. The discovery was made independently by Sir Humphry Davy, in Britain, and Joseph-Louis Gay-Lussac and Louis-Jacques Thenard, in France. The material they created was, however, impure. It was another hundred years before pure boron was isolated.
Sometime before 1812 the term boron was coined by combining bor(ax) with (carb)on. In turn, borax was derived from the Arabic word buraq.
Isotopes
Boron exists in two natural, stable isotopes. Boron-11 accounts for 80.2% of the mix, while boron-10 makes up the remaining 19.8%.
Production
Production of pure elemental boron is very difficult. By passing an electric current through a tantalum filament to heat it, boron bromide or chloride can be reduced with hydrogen. Boron can be produced in at least four crystalline structures or allotropes.
When pure boron is produced it is almost chemically inert. It is, therefore, more useful to produce and use boron compounds than pure boron. These compounds include borax (sodium tetraborate) and boric acid (also called boracic or orthoboric acid).
Boron also forms compounds with carbon (boron carbide) and nitrogen (boron nitride). Several series of compounds can be formed with boron and various metals (borides), hydrogen (boranes) and the halogens (trihalides).
Uses
Boron compounds have numerous uses. Small quantities of boron, usually in boric acid or borate compounds, are essential for the growth of healthy land plants. Boron deficiency can lead to disorders such as brown heart.
Boric acid also has medical uses. It is an ingredient in eye lotions and can be used as an antiseptic for burns. Other uses include electroplating nickel, tanning leather and as a fire-retardant in some fabrics.
Glassware for use in laboratory or cooking equipment is created by mixing silica with boron oxide to produce a heat-resistant borosilicate glass. Borax can be used as a soldering flux and as an ingredient in soaps.
Boron can be used with many metals. With iron, as a ferroboron alloy, it can increase the hardness of steel, with aluminium it can refine the grain in castings and with copper it is used as a degasifier. Boron’s semiconductor properties allow it to be mixed with silicon or germanium to modify their electrical conductivity.
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Related Elements
Hydrogen (H), Carbon (C), Nitrogen (N), Oxygen (O), Sodium (Na), Aluminium / Aluminum (Al), Silicon (Si), Chlorine (Cl), Potassium (K), Iron (Fe), Nickel (Ni), Copper (Cu), Germanium (Ge), Bromine (Br), Tantalum (Ta)
