Beryllium (4)

Beryllium is a Group 2 (IIA) element. It is a metal and has a high melting point. At ordinary temperatures, beryllium resists oxidation in air. Beryllium compounds are very toxic. Its ability to scratch glass is probably due to the formation of a thin layer of the oxide. Aquamarine and emerald are precious forms of the mineral beryl, [Be3Al2(SiO3)6].

Its chemistry is dominated by its tendency to lose an electron to form Be2+. As this ion is so small it is highly polarizing, so that its compounds are rather covalent; its small size means that its complexes tend to be tetrahedral rather than octahedral.

•Name: Beryllium
•Symbol: Be
•Atomic number: 4
•Atomic weight: 9.012182
•Standard state: solid at 298 K
•CAS Registry ID: 7440-41-7
•Group in periodic table: 2
•Group name: Alkaline earth metal
•Period in periodic table: 2
•Block in periodic table: s-block
•Color: lead grey
•Classification: Metallic

Historical information

Beryllium was discovered by Nicholas Louis Vauquelin (1763-1829) at 1797 in France. Origin of name: from the Greek word "beryllos" meaning "beryl." Emeralds and beryl were both known to early Egyptians but it was not realized until the end of the 18th century that they are the same mineral, now called beryllium aluminum silicate: [Be3Al2(SiO3)6]. The element was recognized by M.-L. Vauquelin, in 1798, in beryl and emeralds. The metal was isolated much later on in 1828 by Friederich Wöhler (and independently by A.-A.B. Bussy) by the action of potassium on BeCl2 in a platinum crucible.

Physical properties

•Melting point: 1560 [or 1287 °C (2349 °F)] K
•Boiling point: 2742 [or 2469 °C (4476 °F)] K
•Density of solid: 1848 kg m-3

Orbital properties

•Ground state electron configuration: [He].2s2
•Shell structure: 2.2
•Term symbol: 1S0
•Pauling electronegativity: 1.57 (Pauling units)

Isolation

Beryllium metal is available commercially and so would never normally be made in the laboratory. Its extraction from ores is complex. The mineral beryl, [Be3Al2(SiO3)6] is the most important source of beryllium. It is roasted with sodium hexafluorosilicate, Na2SiF6, at 700°C to form beryllium fluoride. This is water soluble and the beryllium may be precipitated as the hydroxide Be(OH)2 by adjustment of the pH to 12.

Pure beryllium may be obtained by electrolysis of molten BeCl2 containing some NaCl. The salt is added since the molten BeCl2 conducts very poorly. Another method involves the reduction of beryllium fluoride with magnesium at 1300°C.

BeF2 + Mg → MgF2