Element 4" redirects here. For the music group, see Elementfour.
Posted 9 months ago in Other.
118 Unique Visitors
"Element 4" redirects here. For the music group, see Elementfour.
Beryllium is a chemical element with symbol Be and atomic number 4. It is a relatively rareelement in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Within the cores of stars beryllium is depleted as it is fused and creates larger elements. 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, 4Be￼BerylliumPronunciation/bəˈrɪliəm/ (bə-RIL-ee-əm)Appearancewhite-gray metallicStandard atomic weight Ar, std(Be)9.0121831(5)Beryllium in the periodic table
Mglithium ← beryllium → boronAtomic number (Z)4Groupgroup 2 (alkaline earth metals)Periodperiod 2Blocks-blockElement category alkaline earth metalElectron configuration[He] 2s2
Electrons per shell
2, 2Physical propertiesPhase at STPsolidMelting point1560 K (1287 °C, 2349 °F)Boiling point2742 K (2469 °C, 4476 °F)Density (near r.t.)1.85 g/cm3when liquid (at m.p.)1.690 g/cm3Critical point5205 K, MPa (extrapolated)Heat of fusion12.2 kJ/molHeat of vaporization292 kJ/molMolar heat capacity16.443 J/(mol·K)Vapor pressure
P (Pa)1101001 k10 k100 kat T (K)146216081791202323272742
Atomic propertiesOxidation states+1, +2(an amphoteric oxide)ElectronegativityPauling scale: 1.57Ionization energies
1st: 899.5 kJ/mol
2nd: 1757.1 kJ/mol
3rd: 14,848.7 kJ/mol
Atomic radiusempirical: 112 pmCovalent radius96±3 pmVan der Waals radius153 pm
Spectral lines of berylliumOther propertiesNatural occurrenceprimordialCrystal structurehexagonal close-packed (hcp)
Speed of soundthin rod12,890 m/s (at r.t.)Thermal expansion11.3 µm/(m·K) (at 25 °C)Thermal conductivity200 W/(m·K)Electrical resistivity36 nΩ·m (at 20 °C)Magnetic orderingdiamagneticMagnetic susceptibility−9.0·10−6 cm3/molYoung's modulus287 GPaShear modulus132 GPaBulk modulus130 GPaPoisson ratio0.032Mohs hardness5.5Vickers hardness1670 MPaBrinell hardness590–1320 MPaCAS Number7440-41-7HistoryDiscoveryLouis Nicolas Vauquelin (1798)First isolationFriedrich Wöhler & Antoine Bussy (1828)Main isotopes of berylliumIsotopeAbundanceHalf-life(t1/2)Decay modeProduct7Betrace53.12 dε7Liγ–9Be100%stable10Betrace1.39×106 yβ−10B
Beryllium improves many physical properties when added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron and nickel. Beryllium does not form oxides until it reaches very high temperatures. Tools made of beryllium copperalloys are strong and hard and do not create sparks when they strike a steel surface. In structural applications, the combination of high flexural rigidity, thermal stability, thermal conductivity and low density (1.85 times that of water) make beryllium metal a desirable aerospace material for aircraft components, missiles, spacecraft, and 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 components of particle detectors. The high thermal conductivities of beryllium and beryllium oxide have led to their use in thermal management applications.
The commercial use of beryllium requires the use of appropriate dust control equipment and industrial controls at all times because of the toxicity of inhaled beryllium-containing dusts that can cause a chronic life-threatening allergic disease in some people called berylliosis.
Beryllium is a steel gray and hard metal that is brittle at room temperature and has a close-packed hexagonal crystal structure. It has exceptional stiffness (Young's modulus 287 GPa) and a reasonably high melting point. The modulus of elasticity of beryllium is approximately 50% greater than that of steel. The combination of this modulus and a relatively low density results in an unusually fast sound conduction speed in beryllium – about 12.9 km/s at ambient conditions. Other significant properties are high specific heat (1925 J·kg−1·K−1) and thermal conductivity (216 W·m−1·K−1), which make beryllium the metal with the best heat dissipation characteristics per unit weight. In combination with the relatively low coefficient of linear thermal expansion (11.4×10−6 K−1), these characteristics result in a unique stability under conditions of thermal loading.
Naturally occurring beryllium, save for slight contamination by the cosmogenic radioisotopes, is isotopically pure beryllium-9, which has a nuclear spin of 3/2. Beryllium has a large scattering cross section for high-energy neutrons, about 6 barns for energies above approximately 10 keV. Therefore, it works as a neutron reflector and neutron moderator, effectively slowing the neutrons to the thermal energy range of below 0.03 eV, where the total cross section is at least an order of magnitude lower – exact value strongly depends on the purity and size of the crystallites in the material.
The single primordial beryllium isotope 9Be also undergoes a (n,2n) neutron reaction with neutron energies over about 1.9 MeV, to produce 8Be, which almost immediately breaks into two alpha particles. Thus, for high-energy neutrons, beryllium is a neutron multiplier, releasing more neutrons than it absorbs. This nuclear reaction is:
+ n → 2 4
+ 2 n
Neutrons are liberated when beryllium nucleiare struck by energetic alpha particlesproducing the nuclear reaction
+ n, where 4
is an alpha particle and 12
is a carbon-12 nucleus.
Beryllium also releases neutrons under bombardment by gamma rays. Thus, natural beryllium bombarded either by alphas or gammas from a suitable radioisotope is a key component of most radioisotope-powered nuclear reaction neutron sources for the laboratory production of free neutrons.
Small amounts of tritium are liberated when 9
nuclei absorb low energy neutrons in the three-step nuclear reaction
+ n → 4
+ β−, 6
+ n → 4
Note that 6
has a half-life of only 0.8 seconds, β− is an electron, and 6
has a high neutron absorption cross-section. Tritium is a radioisotope of concern in nuclear reactor waste streams.
As a metal, beryllium is transparent to most wavelengths of X-rays and gamma rays, making it useful for the output windows of X-ray tubes and other such apparatus.
Isotopes and nucleosynthesis
Main article: Isotopes of beryllium
Both stable and unstable isotopes of beryllium are created in stars, but the radioisotopes do not last long. It is believed that most of the stable beryllium in the universe was originally created in the interstellar medium when cosmic raysinduced fission in heavier elements found in interstellar gas and dust. Primordial beryllium contains only one stable isotope, 9Be, and therefore beryllium is a monoisotopic element.
Plot showing variations in solar activity, including variation in sunspot number (red) and 10Be concentration (blue). Note that the beryllium scale is inverted, so increases on this scale indicate lower 10Be levels
Radioactive cosmogenic 10Be is produced in the atmosphere of the Earth by the cosmic ray spallation of oxygen. 10Be accumulates at the soil surface, where its relatively long half-life (1.36 million years) permits a long residence time before decaying to boron-10. Thus, 10Be and its daughter products are used to examine natural soil erosion, soil formationand the development of lateritic soils, and as a proxy for measurement of the variations in solar activity and the age of ice cores. The production of 10Be is inversely proportional to solar activity, because increased solar windduring periods of high solar activity decreases the flux of galactic cosmic rays that reach the Earth. Nuclear explosions also form 10Be by the reaction of fast neutrons with 13C in the carbon dioxide in air. This is one of the indicators of past activity at nuclear weapon test sites. The isotope 7Be (half-life 53 days) is also cosmogenic, and shows an atmospheric abundance linked to sunspots, much like 10Be.
8Be has a very short half-life of about 7×10−17 s that contributes to its significant cosmological role, as elements heavier than beryllium could not have been produced by nuclear fusion in the Big Bang. This is due to the lack of sufficient time during the Big Bang's nucleosynthesis phase to produce carbon by the fusion of 4He nuclei and the very low concentrations of available beryllium-8. The British astronomer Sir Fred Hoyle first showed that the energy levels of 8Be and 12C allow carbon production by the so-called triple-alpha process in helium-fueled stars where more nucleosynthesis time is available. This process allows carbon to be produced in stars, but not in the Big Bang. Star-created carbon (the basis of carbon-based life) is thus a component in the elements in the gas and dust ejected by AGB stars and supernovae(see also Big Bang nucleosynthesis), as well as the creation of all other elements with atomic numbers larger than that of carbon.
The 2s electrons of beryllium may contribute to chemical bonding. Therefore, when 7Be decays by L-electron capture, it does so by taking electrons from its atomic orbitals that may be participating in bonding. This makes its decay rate dependent to a measurable degree upon its chemical surroundings – a rare occurrence in nuclear decay.
The shortest-lived known isotope of beryllium is 13Be which decays through neutron emission. It has a half-life of 2.7 × 10−21 s. 6Be is also very short-lived with a half-life of 5.0 × 10−21 s. The exotic isotopes 11Be and 14Be are known to exhibit a nuclear halo.This phenomenon can be understood as the nuclei of 11Be and 14Be have, respectively, 1 and 4 neutrons orbiting substantially outside the classical Fermi 'waterdrop' model of the nucleus.
Beryllium ore with 1US¢ coin for scale
Emerald is a naturally occurring compoundof beryllium.
The Sun has a concentration of 0.1 parts per billion (ppb) of beryllium. Beryllium has a concentration of 2 to 6 parts per million (ppm) in the Earth's crust. It is most concentrated in the soils, 6 ppm. Trace amounts of 9Be are found in the Earth's atmosphere. The concentration of beryllium in sea water is 0.2–0.6 parts per trillion. In stream water, however, beryllium is more abundant with a concentration of 0.1 ppb.
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, red beryl 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.[