Beryllium

Beryllium is the chemical element with the symbol Be and atomic number 4. Because any beryllium synthesized in stars is short-lived, it is a relatively rare element in both the universe and in the crust of the Earth. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. As a free element it is a steel-gray, strong, lightweight and brittle alkaline earth metal.

Beryllium increases hardness and resistance to corrosion when alloyed to aluminium, cobalt, copper (notably beryllium copper), iron and nickel. In structural applications, high flexural rigidity, thermal stability, thermal conductivity and low density (1.85 times that of water) make beryllium a quality aerospace material for high-speed aircraft, missiles, space vehicles and communication satellites. Because of its low density and atomic mass, beryllium is relatively transparent to X-rays and other forms of ionizing radiation; therefore, it is the most common window material for X-ray equipment and in particle physics experiments. The high thermal conductivities of beryllium and beryllium oxide have led to their use in heat transport and heat sinking applications.

The commercial use of beryllium metal presents technical challenges due to the toxicity (especially by inhalation) of beryllium-containing dusts. Beryllium is corrosive to tissue, and can cause a chronic life-threatening allergic disease called berylliosis in some people. The element is not known to be necessary or useful for either plant or animal life.

Occurrence

Beryllium has a concentration of 2 to 6 parts per million (ppm) in the Earth's crust. The Sun has a concentration of 0.1 parts per billion (ppb) of beryllium. It is most concentrated in the soils, 6 ppm, and is found in 0.2 parts per trillion (ppt) of sea water. Trace amounts of 9Be are found in the Earth's atmosphere. In sea water, beryllium is exceedingly rare, comprising only 0.0006 ppb by weight. In stream water, however, beryllium is more abundant with 0.1 ppb by weight.

Beryllium is found in over 100 minerals, but most are uncommon to rare. The more common beryllium containing minerals include: bertrandite (Be4Si2O7(OH)2), beryl (Al2Be3Si6O18), chrysoberyl (Al2BeO4) and phenakite (Be2SiO4). Precious forms of beryl are aquamarine, bixbite and emerald. The green color in gem-quality forms of beryl comes from varying amounts of chromium (about 2% for emerald).

The two main ores of beryllium, beryl and bertrandite, are found in Argentina, Brazil, India, Madagascar, Russia and the United States. Total world reserves of beryllium ore are greater than 400,000 tonnes.

Symbol		Be
Atomic Number		4
Atomic Weight		9.01218
Oxidation States		+2
Electronegativity, Pauling		1.57
State at RT		Solid, Metal
Melting Point, K		1551
Boiling Point, K		3243

Appearance and Characteristics

Harmful effects:

Beryllium and its salts are both toxic and carcinogenic.

Characteristics:

• Beryllium is light, silver-gray, relatively soft metal that is strong but brittle.

• Beryllium has the highest melting point of the light metals, melting at 1278 oC – considerably higher than, for example, Lithium (180 oC) Sodium (98 oC) Magnesium (650 oC) Aluminum (660 oC) or Calcium (839 oC).

• Under normal conditions, a thin layer of the hard oxide BeO forms on beryllium’s surface, protecting the metal from further attack by water or air.

• As a result of this BeO layer, beryllium does not oxidize in air even at 600oC and it resists corrosion by concentrated nitric acid.

• Beryllium also has high thermal conductivity and is nonmagnetic.

Uses of Beryllium

• Unlike most metals, beryllium is virtually transparent to x-rays and hence it is used in radiation windows for x-ray tubes.

• Beryllium alloys are used in the aerospace industry as light-weight materials for high performance aircraft, satellites and spacecraft.

• Beryllium is used as an alloy with copper to make spark-proof tools.

• Beryllium is also used in nuclear reactors as a reflector and absorber of neutrons, a shield and a moderator.