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Beryllium

Beryllium is a chemical element; it has symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form minerals. Gemstones high in beryllium include beryl (aquamarine, emerald, red beryl) and chrysoberyl. It is a relatively rare element 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 into heavier elements. Beryllium constitutes about 0.0004 percent by mass of Earth's crust. The world's annual beryllium production of 220 tons is usually manufactured by extraction from the mineral beryl, a difficult process because beryllium bonds strongly to oxygen.

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. When added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron, or nickel, beryllium improves many physical properties. For example, tools and components made of beryllium copper alloys are strong and hard and do not create sparks when they strike a steel surface. In air, the surface of beryllium oxidizes readily at room temperature to form a passivation layer 1–10 nm thick that protects it from further oxidation and corrosion. The metal oxidizes in bulk (beyond the passivation layer) when heated above 500 C, and burns brilliantly when heated to about 2500 C.

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, berylliosis, in some people. Berylliosis causes pneumonia and other associated respiratory illness.

Physical properties
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 melting point of 1287 °C. The modulus of elasticity of beryllium is approximately 35% 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 ($1,925 J·kg^{−1}·K^{−1}$) 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.

Nuclear properties
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; the 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 + 2 n

Neutrons are liberated when beryllium nuclei are struck by energetic alpha particles producing the nuclear reaction
 * + →  + n

where is an alpha particle and  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 nuclei absorb low energy neutrons in the three-step nuclear reaction
 * + n → +,     →  + β−,     + n →  +

has a half-life of only 0.8 seconds, β− is an electron, and has a high neutron absorption cross section. Tritium is a radioisotope of concern in nuclear reactor waste streams.

Optical properties
As a metal, beryllium is transparent or translucent 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
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 rays induced fission in heavier elements found in interstellar gas and dust. Primordial beryllium contains only one stable isotope, 9Be, and therefore beryllium is, uniquely among all stable elements with an even atomic number, a monoisotopic and mononuclidic element.

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 formation and 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 wind during 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 8 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. 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 16Be, which decays through neutron emission with a half-life of $6.5 s$. 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.

Occurrence
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 the 47th most abundant element in the 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.

Production
The extraction of beryllium from its compounds is a difficult process due to its high affinity for oxygen at elevated temperatures, and its ability to reduce water when its oxide film is removed. Currently the United States, China and Kazakhstan are the only three countries involved in the industrial-scale extraction of beryllium. Kazakhstan produces beryllium from a concentrate stockpiled before the breakup of the Soviet Union around 1991. This resource had become nearly depleted by mid-2010s.

Production of beryllium in Russia was halted in 1997, and is planned to be resumed in the 2020s.

Beryllium is most commonly extracted from the mineral beryl, which is either sintered using an extraction agent or melted into a soluble mixture. The sintering process involves mixing beryl with sodium fluorosilicate and soda at 770 C to form sodium fluoroberyllate, aluminium oxide and silicon dioxide. Beryllium hydroxide is precipitated from a solution of sodium fluoroberyllate and sodium hydroxide in water. The extraction of beryllium using the melt method involves grinding beryl into a powder and heating it to 1650 C. The melt is quickly cooled with water and then reheated 250 to 300 C in concentrated sulfuric acid, mostly yielding beryllium sulfate and aluminium sulfate. Aqueous ammonia is then used to remove the aluminium and sulfur, leaving beryllium hydroxide.

Beryllium hydroxide created using either the sinter or melt method is then converted into beryllium fluoride or beryllium chloride. To form the fluoride, aqueous ammonium hydrogen fluoride is added to beryllium hydroxide to yield a precipitate of ammonium tetrafluoroberyllate, which is heated to 1000 C to form beryllium fluoride. Heating the fluoride to 900 C with magnesium forms finely divided beryllium, and additional heating to 1300 C creates the compact metal. Heating beryllium hydroxide forms the oxide, which becomes beryllium chloride when combined with carbon and chlorine. Electrolysis of molten beryllium chloride is then used to obtain the metal.

Chemical properties
A beryllium atom has the electronic configuration [He] 2s2. The predominant oxidation state of beryllium is +2; the beryllium atom has lost both of its valence electrons. Lower oxidation states complexes of beryllium are exceedingly rare. For example, bis(carbene) compounds proposed to contain beryllium in the 0- and +1-oxidation state have been reported, although these claims have proved controversial. A stable complex with a Be-Be bond, which formally features beryllium in the +1 oxidation state, has been described. Beryllium's chemical behavior is largely a result of its small atomic and ionic radii. It thus has very high ionization potentials and strong polarization while bonded to other atoms, which is why all of its compounds are covalent. Its chemistry has similarities to that of aluminium, an example of a diagonal relationship.

At room temperature, the surface of beryllium forms a 1−10 nm-thick oxide passivation layer that prevents further reactions with air, except for gradual thickening of the oxide up to about 25 nm. When heated above about 500 °C, oxidation into the bulk metal progresses along grain boundaries. Once the metal is ignited in air by heating above the oxide melting point around 2500 °C, beryllium burns brilliantly, forming a mixture of beryllium oxide and beryllium nitride. Beryllium dissolves readily in non-oxidizing acids, such as HCl and diluted H2SO4, but not in nitric acid or water as this forms the oxide. This behavior is similar to that of aluminium. Beryllium also dissolves in alkali solutions.

Binary compounds of beryllium(II) are polymeric in the solid state. BeF2 has a silica-like structure with corner-shared BeF4 tetrahedra. BeCl2 and BeBr2 have chain structures with edge-shared tetrahedra. Beryllium oxide, BeO, is a white refractory solid which has a wurtzite crystal structure and a thermal conductivity as high as some metals. BeO is amphoteric. Beryllium sulfide, selenide and telluride are known, all having the zincblende structure. Beryllium nitride, Be3N2, is a high-melting-point compound which is readily hydrolyzed. Beryllium azide, BeN6 is known and beryllium phosphide, Be3P2 has a similar structure to Be3N2. A number of beryllium borides are known, such as Be5B, Be4B, Be2B, BeB2, BeB6 and BeB12. Beryllium carbide, Be2C, is a refractory brick-red compound that reacts with water to give methane. No beryllium silicide has been identified.

The halides BeX2 (X = F, Cl, Br, and I) have a linear monomeric molecular structure in the gas phase. Complexes of the halides are formed with one or more ligands donating a total of two pairs of electrons. Such compounds obey the octet rule. Other 4-coordinate complexes, such as the aqua-ion [Be(H2O)4]2+ also obey the octet rule.

Aqueous solutions

Solutions of beryllium salts, such as beryllium sulfate and beryllium nitrate, are acidic because of hydrolysis of the [Be(H2O)4]2+ ion. The concentration of the first hydrolysis product, [Be(H2O)3(OH)]+, is less than 1% of the beryllium concentration. The most stable hydrolysis product is the trimeric ion [Be3(OH)3(H2O)6]3+. Beryllium hydroxide, Be(OH)2, is insoluble in water at pH 5 or more. Consequently, beryllium compounds are generally insoluble at biological pH. Because of this, inhalation of beryllium metal dust by people leads to the development of the fatal condition of berylliosis. Be(OH)2 dissolves in strongly alkaline solutions.

Beryllium(II) forms few complexes with monodentate ligands because the water molecules in the aquo-ion, [Be(H2O)4]2+ are bound very strongly to the beryllium ion. Notable exceptions are the series of water-soluble complexes with the fluoride ion:

Beryllium (II) forms many complexes with bidentate ligands containing oxygen-donor atoms. The species [Be3O(H2PO4)6]2- is notable for having a 3-coordinate oxide ion at its center. Basic beryllium acetate, Be4O(OAc)6, has an oxide ion surrounded by a tetrahedron of beryllium atoms.

With organic ligands, such as the malonate ion, the acid deprotonates when forming the complex. The donor atoms are two oxygens. The formation of a complex is in competition with the metal ion-hydrolysis reaction and mixed complexes with both the anion and the hydroxide ion are also formed. For example, derivatives of the cyclic trimer are known, with a bidentate ligand replacing one or more pairs of water molecules.

Aliphatic hydroxycarboxylic acids such as glycollic acid form rather weak monodentate complexes in solution, in which the hydroxyl group remains intact. In the solid state, the hydroxyl group may deprotonate: a hexamer,, was isolated long ago. Aromatic hydroxy ligands (i.e. phenols) form relatively strong complexes. For example, log K1 and log K2 values of 12.2 and 9.3 have been reported for complexes with tiron.

Beryllium has generally a rather poor affinity for ammine ligands. Ligands such as EDTA behave as dicarboxylic acids. There are many early reports of complexes with amino acids, but unfortunately they are not reliable as the concomitant hydrolysis reactions were not understood at the time of publication. Values for log β of ca. 6 to 7 have been reported. The degree of formation is small because of competition with hydrolysis reactions.

Organic chemistry
Organoberyllium chemistry is limited to academic research due to the cost and toxicity of beryllium, beryllium derivatives and reagents required for the introduction of beryllium, such as beryllium chloride. Organometallic beryllium compounds are known to be highly reactive Examples of known organoberyllium compounds are dineopentylberyllium, beryllocene (Cp2Be),   diallylberyllium (by exchange reaction of diethyl beryllium with triallyl boron), bis(1,3-trimethylsilylallyl)beryllium, Be(mes)2, and (beryllium(I) complex) diberyllocene. Ligands can also be aryls and alkynyls.

History
The mineral beryl, which contains beryllium, has been used at least since the Ptolemaic dynasty of Egypt. In the first century CE, Roman naturalist Pliny the Elder mentioned in his encyclopedia Natural History that beryl and emerald ("smaragdus") were similar. The Papyrus Graecus Holmiensis, written in the third or fourth century CE, contains notes on how to prepare artificial emerald and beryl.

Early analyses of emeralds and beryls by Martin Heinrich Klaproth, Torbern Olof Bergman, Franz Karl Achard, and Johann Jakob Bindheim always yielded similar elements, leading to the mistaken conclusion that both substances are aluminium silicates. Mineralogist René Just Haüy discovered that both crystals are geometrically identical, and he asked chemist Louis-Nicolas Vauquelin for a chemical analysis.

In a 1798 paper read before the Institut de France, Vauquelin reported that he found a new "earth" by dissolving aluminium hydroxide from emerald and beryl in an additional alkali. The editors of the journal Annales de Chimie et de Physique named the new earth "glucine" for the sweet taste of some of its compounds. Klaproth preferred the name "beryllina" due to the fact that yttria also formed sweet salts. The name "beryllium" was first used by Wöhler in 1828.

Friedrich Wöhler and Antoine Bussy independently isolated beryllium in 1828 by the chemical reaction of metallic potassium with beryllium chloride, as follows:
 * BeCl2 + 2 K → 2 KCl + Be

Using an alcohol lamp, Wöhler heated alternating layers of beryllium chloride and potassium in a wired-shut platinum crucible. The above reaction immediately took place and caused the crucible to become white hot. Upon cooling and washing the resulting gray-black powder, he saw that it was made of fine particles with a dark metallic luster. The highly reactive potassium had been produced by the electrolysis of its compounds, a process discovered 21 years earlier. The chemical method using potassium yielded only small grains of beryllium from which no ingot of metal could be cast or hammered.

The direct electrolysis of a molten mixture of beryllium fluoride and sodium fluoride by Paul Lebeau in 1898 resulted in the first pure (99.5 to 99.8%) samples of beryllium. However, industrial production started only after the First World War. The original industrial involvement included subsidiaries and scientists related to the Union Carbide and Carbon Corporation in Cleveland, Ohio, and Siemens & Halske AG in Berlin. In the US, the process was ruled by Hugh S. Cooper, director of The Kemet Laboratories Company. In Germany, the first commercially successful process for producing beryllium was developed in 1921 by Alfred Stock and Hans Goldschmidt.

A sample of beryllium was bombarded with alpha rays from the decay of radium in a 1932 experiment by James Chadwick that uncovered the existence of the neutron. This same method is used in one class of radioisotope-based laboratory neutron sources that produce 30 neutrons for every million α particles.

Beryllium production saw a rapid increase during World War II due to the rising demand for hard beryllium-copper alloys and phosphors for fluorescent lights. Most early fluorescent lamps used zinc orthosilicate with varying content of beryllium to emit greenish light. Small additions of magnesium tungstate improved the blue part of the spectrum to yield an acceptable white light. Halophosphate-based phosphors replaced beryllium-based phosphors after beryllium was found to be toxic.

Electrolysis of a mixture of beryllium fluoride and sodium fluoride was used to isolate beryllium during the 19th century. The metal's high melting point makes this process more energy-consuming than corresponding processes used for the alkali metals. Early in the 20th century, the production of beryllium by the thermal decomposition of beryllium iodide was investigated following the success of a similar process for the production of zirconium, but this process proved to be uneconomical for volume production.

Pure beryllium metal did not become readily available until 1957, even though it had been used as an alloying metal to harden and toughen copper much earlier. Beryllium could be produced by reducing beryllium compounds such as beryllium chloride with metallic potassium or sodium. Currently, most beryllium is produced by reducing beryllium fluoride with magnesium. The price on the American market for vacuum-cast beryllium ingots was about $338 per pound ($745 per kilogram) in 2001.

Between 1998 and 2008, the world's production of beryllium had decreased from 343 to about 200 tonnes. It then increased to 230 metric tons by 2018, of which 170 tonnes came from the United States.

Etymology
Beryllium was named for the semiprecious mineral beryl, from which it was first isolated.

Radiation windows
Because of its low atomic number and very low absorption for X-rays, the oldest and still one of the most important applications of beryllium is in radiation windows for X-ray tubes. Extreme demands are placed on purity and cleanliness of beryllium to avoid artifacts in the X-ray images. Thin beryllium foils are used as radiation windows for X-ray detectors, and their extremely low absorption minimizes the heating effects caused by high-intensity, low energy X-rays typical of synchrotron radiation. Vacuum-tight windows and beam-tubes for radiation experiments on synchrotrons are manufactured exclusively from beryllium. In scientific setups for various X-ray emission studies (e.g., energy-dispersive X-ray spectroscopy) the sample holder is usually made of beryllium because its emitted X-rays have much lower energies (≈100 eV) than X-rays from most studied materials.

Low atomic number also makes beryllium relatively transparent to energetic particles. Therefore, it is used to build the beam pipe around the collision region in particle physics setups, such as all four main detector experiments at the Large Hadron Collider (ALICE, ATLAS, CMS, LHCb), the Tevatron and at SLAC. The low density of beryllium allows collision products to reach the surrounding detectors without significant interaction, its stiffness allows a powerful vacuum to be produced within the pipe to minimize interaction with gases, its thermal stability allows it to function correctly at temperatures of only a few degrees above absolute zero, and its diamagnetic nature keeps it from interfering with the complex multipole magnet systems used to steer and focus the particle beams.

Mechanical applications
Because of its stiffness, light weight and dimensional stability over a wide temperature range, beryllium metal is used for lightweight structural components in the defense and aerospace industries in high-speed aircraft, guided missiles, spacecraft, and satellites, including the James Webb Space Telescope. Several liquid-fuel rockets have used rocket nozzles made of pure beryllium. Beryllium powder was itself studied as a rocket fuel, but this use has never materialized. A small number of extreme high-end bicycle frames have been built with beryllium. From 1998 to 2000, the McLaren Formula One team used Mercedes-Benz engines with beryllium-aluminium-alloy pistons. The use of beryllium engine components was banned following a protest by Scuderia Ferrari.

Mixing about 2.0% beryllium into copper forms an alloy called beryllium copper that is six times stronger than copper alone. Beryllium alloys are used in many applications because of their combination of elasticity, high electrical conductivity and thermal conductivity, high strength and hardness, nonmagnetic properties, as well as good corrosion and fatigue resistance. These applications include non-sparking tools that are used near flammable gases (beryllium nickel) in springs and membranes (beryllium nickel and beryllium iron) used in surgical instruments and high temperature devices. As little as 50 parts per million of beryllium alloyed with liquid magnesium leads to a significant increase in oxidation resistance and decrease in flammability.

The high elastic stiffness of beryllium has led to its extensive use in precision instrumentation, e.g. in inertial guidance systems and in the support mechanisms for optical systems. Beryllium-copper alloys were also applied as a hardening agent in "Jason pistols", which were used to strip the paint from the hulls of ships.

In sound amplification systems, the speed at which sound travels directly affects the resonant frequency of the amplifier, thereby influencing the range of audible high-frequency sounds. Beryllium stands out due to its exceptionally high speed of sound propagation compared to other metals. This unique property allows beryllium to achieve higher resonant frequencies, making it an ideal material for use as a diaphragm in high-quality loudspeakers.

Beryllium was also used for cantilevers in high-performance phonograph cartridge styli, where its extreme stiffness and low density allowed for tracking weights to be reduced to 1 gram while still tracking high frequency passages with minimal distortion.

An earlier major application of beryllium was in brakes for military airplanes because of its hardness, high melting point, and exceptional ability to dissipate heat. Environmental considerations have led to substitution by other materials.

To reduce costs, beryllium can be alloyed with significant amounts of aluminium, resulting in the AlBeMet alloy (a trade name). This blend is cheaper than pure beryllium, while still retaining many desirable properties.

Mirrors
Beryllium mirrors are of particular interest. Large-area mirrors, frequently with a honeycomb support structure, are used, for example, in meteorological satellites where low weight and long-term dimensional stability are critical. Smaller beryllium mirrors are used in optical guidance systems and in fire-control systems, e.g. in the German-made Leopard 1 and Leopard 2 main battle tanks. In these systems, very rapid movement of the mirror is required, which again dictates low mass and high rigidity. Usually the beryllium mirror is coated with hard electroless nickel plating which can be more easily polished to a finer optical finish than beryllium. In some applications, though, the beryllium blank is polished without any coating. This is particularly applicable to cryogenic operation where thermal expansion mismatch can cause the coating to buckle.

The James Webb Space Telescope has 18 hexagonal beryllium sections for its mirrors, each plated with a thin layer of gold. Because JWST will face a temperature of 33 K, the mirror is made of gold-plated beryllium, which is capable of handling extreme cold better than glass. Beryllium contracts and deforms less than glass and remains more uniform – in such temperatures. For the same reason, the optics of the Spitzer Space Telescope are entirely built of beryllium metal.

Magnetic applications

Beryllium is non-magnetic. Therefore, tools fabricated out of beryllium-based materials are used by naval or military explosive ordnance disposal teams for work on or near naval mines, since these mines commonly have magnetic fuzes. They are also found in maintenance and construction materials near magnetic resonance imaging (MRI) machines because of the high magnetic fields generated. In the fields of radio communications and powerful (usually military) radars, hand tools made of beryllium are used to tune the highly magnetic klystrons, magnetrons, traveling wave tubes, etc., that are used for generating high levels of microwave power in the transmitters.

Nuclear applications
Thin plates or foils of beryllium are sometimes used in nuclear weapon designs as the very outer layer of the plutonium pits in the primary stages of thermonuclear bombs, placed to surround the fissile material. These layers of beryllium are good "pushers" for the implosion of the plutonium-239, and they are good neutron reflectors, just as in beryllium-moderated nuclear reactors.

Beryllium is also commonly used in some neutron sources in laboratory devices in which relatively few neutrons are needed (rather than having to use a nuclear reactor or a particle accelerator-powered neutron generator). For this purpose, a target of beryllium-9 is bombarded with energetic alpha particles from a radioisotope such as polonium-210, radium-226, plutonium-238, or americium-241. In the nuclear reaction that occurs, a beryllium nucleus is transmuted into carbon-12, and one free neutron is emitted, traveling in about the same direction as the alpha particle was heading. Such alpha decay-driven beryllium neutron sources, named "urchin" neutron initiators, were used in some early atomic bombs. Neutron sources in which beryllium is bombarded with gamma rays from a gamma decay radioisotope, are also used to produce laboratory neutrons.

Beryllium is also used in fuel fabrication for CANDU reactors. The fuel elements have small appendages that are resistance brazed to the fuel cladding using an induction brazing process with Be as the braze filler material. Bearing pads are brazed in place to prevent contact between the fuel bundle and the pressure tube containing it, and inter-element spacer pads are brazed on to prevent element to element contact.

Beryllium is also used at the Joint European Torus nuclear-fusion research laboratory, and it will be used in the more advanced ITER to condition the components which face the plasma. Beryllium has also been proposed as a cladding material for nuclear fuel rods, because of its good combination of mechanical, chemical, and nuclear properties. Beryllium fluoride is one of the constituent salts of the eutectic salt mixture FLiBe, which is used as a solvent, moderator and coolant in many hypothetical molten salt reactor designs, including the liquid fluoride thorium reactor (LFTR).

Acoustics
The low weight and high rigidity of beryllium make it useful as a material for high-frequency speaker drivers. Because beryllium is expensive (many times more than titanium), hard to shape due to its brittleness, and toxic if mishandled, beryllium tweeters are limited to high-end home,  pro audio, and public address applications. Some high-fidelity products have been fraudulently claimed to be made of the material.

Some high-end phonograph cartridges used beryllium cantilevers to improve tracking by reducing mass.

Electronic
Beryllium is a p-type dopant in III-V compound semiconductors. It is widely used in materials such as GaAs, AlGaAs, InGaAs and InAlAs grown by molecular beam epitaxy (MBE). Cross-rolled beryllium sheet is an excellent structural support for printed circuit boards in surface-mount technology. In critical electronic applications, beryllium is both a structural support and heat sink. The application also requires a coefficient of thermal expansion that is well matched to the alumina and polyimide-glass substrates. The beryllium-beryllium oxide composite "E-Materials" have been specially designed for these electronic applications and have the additional advantage that the thermal expansion coefficient can be tailored to match diverse substrate materials.

Beryllium oxide is useful for many applications that require the combined properties of an electrical insulator and an excellent heat conductor, with high strength and hardness and a very high melting point. Beryllium oxide is frequently used as an insulator base plate in high-power transistors in radio frequency transmitters for telecommunications. Beryllium oxide is also being studied for use in increasing the thermal conductivity of uranium dioxide nuclear fuel pellets. Beryllium compounds were used in fluorescent lighting tubes, but this use was discontinued because of the disease berylliosis which developed in the workers who were making the tubes.

Healthcare
Beryllium is a component of several dental alloys.

Biological effects
Approximately 35 micrograms of beryllium is found in the average human body, an amount not considered harmful. Beryllium is chemically similar to magnesium and therefore can displace it from enzymes, which causes them to malfunction. Because Be2+ is a highly charged and small ion, it can easily get into many tissues and cells, where it specifically targets cell nuclei, inhibiting many enzymes, including those used for synthesizing DNA. Its toxicity is exacerbated by the fact that the body has no means to control beryllium levels, and once inside the body, beryllium cannot be removed.

Inhalation
Chronic beryllium disease (CBD), or berylliosis, is a pulmonary and systemic granulomatous disease caused by inhalation of dust or fumes contaminated with beryllium; either large amounts over a short time or small amounts over a long time can lead to this ailment. Symptoms of the disease can take up to five years to develop; about a third of patients with it die and the survivors are left disabled. The International Agency for Research on Cancer (IARC) lists beryllium and beryllium compounds as Category 1 carcinogens.

Occupational exposure
In the US, the Occupational Safety and Health Administration (OSHA) has designated a permissible exposure limit (PEL) for beryllium and beryllium compounds of 0.2 μg/m3 as an 8-hour time-weighted average (TWA) and 2.0 μg/m3 as a short-term exposure limit over a sampling period of 15 minutes. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) upper-bound threshold of 0.5 μg/m3. The IDLH (immediately dangerous to life and health) value is 4 mg/m3. The toxicity of beryllium is on par with other toxic metalloids/metals, such as arsenic and mercury.

Exposure to beryllium in the workplace can lead to a sensitized immune response and, over time develop berylliosis. The National Institute for Occupational Safety and Health (NIOSH) in the United States researches these effects in collaboration with a major manufacturer of beryllium products. NIOSH also conducts genetic research on sensitization and CBD, independently of this collaboration.

Acute beryllium disease in the form of chemical pneumonitis was first reported in Europe in 1933 and in the United States in 1943. A survey found that about 5% of workers in plants manufacturing fluorescent lamps in 1949 in the United States had beryllium-related lung diseases. Chronic berylliosis resembles sarcoidosis in many respects, and the differential diagnosis is often difficult. It killed some early workers in nuclear weapons design, such as Herbert L. Anderson.

Beryllium may be found in coal slag. When the slag is formulated into an abrasive agent for blasting paint and rust from hard surfaces, the beryllium can become airborne and become a source of exposure.

Although the use of beryllium compounds in fluorescent lighting tubes was discontinued in 1949, potential for exposure to beryllium exists in the nuclear and aerospace industries, in the refining of beryllium metal and the melting of beryllium-containing alloys, in the manufacturing of electronic devices, and in the handling of other beryllium-containing material.

Detection
Early researchers undertook the highly hazardous practice of identifying beryllium and its various compounds from its sweet taste. A modern test for beryllium in air and on surfaces has been developed and published as an international voluntary consensus standard, ASTM D7202. The procedure uses dilute ammonium bifluoride for dissolution and fluorescence detection with beryllium bound to sulfonated hydroxybenzoquinoline, allowing up to 100 times more sensitive detection than the recommended limit for beryllium concentration in the workplace. Fluorescence increases with increasing beryllium concentration. The new procedure has been successfully tested on a variety of surfaces and is effective for the dissolution and detection of refractory beryllium oxide and siliceous beryllium in minute concentrations (ASTM D7458). The NIOSH Manual of Analytical Methods contains methods for measuring occupational exposures to beryllium.

title: Beryllium


text:
Wikipedia talk:WikiProject Elements

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"Range of variation" column
Sometimes it is filled with something, sometimes it is merged with the "Normal proportion" column. But most of the time, it just leaved blank. Why this column exist when it is completely empty in that isotopes page?

Completely deleting this column to all pages might be too disruptive, but IMHO this column can be removed for mononuclidic elements. There is only one isotope with abundance 100% for them, so they don't need this column. --Nucleus hydro elemon (talk) 06:50, 1 May 2024 (UTC)
 * I agree for mononuclidic elements. As for the others, maybe at some point they'll stop being empty as IUPAC turns more atomic weights into intervals, but that'll take a while and might not affect all elements. Double sharp (talk) 15:27, 29 May 2024 (UTC)
 * I deleted that column for those 21 mononuclidic elements. Nucleus hydro elemon (talk) 06:26, 18 June 2024 (UTC)

How to help best
Hey there, I recently discovered this WikiProject and I'd really like to contribute to the good work that is being done here. I have looked around on the project pages, and am wondering what I could do that would be most useful. Should I adopt one of the element/period/group pages that are not GA yet (and not actively worked on by a project member) and focus on improving it? Patrol the recent changes on the pages followed by the project? Something else that is crucial but not obvious at first glance? A bit of everything? Thanks! Choucas Bleu (T·C) 14:40, 1 May 2024 (UTC)

 * I think you should edit pages that you are most interested in. Every edit adds that page to your "watch" list. Also "watch" this page. I expect your list of topics will grow over time.
 * In case it is helpful, there is a tool for look for most-visited pages by category:
 * Popular pages: Most visited pages in Elements during April 2024
 * Popular "C" rated pages (where big improvements are easiest) Most visited "C" pages in Elements during April 2024
 * Johnjbarton (talk) 15:05, 1 May 2024 (UTC)
 * Thank you for linking the tool, it is indeed quite helpful. Choucas Bleu  (T·C) 15:26, 1 May 2024 (UTC)
 * Hi! This is an effort initiated and continued by volunteers. People enjoy themselves here, so you should, too. Other editors will be genuinely glad to assist you in your effort if they can :)
 * What do you want from this project? As for me, I joined this project because I hoped to increase my knowledge of chemistry (surprisingly, it didn't really have this effect, and some other editors here know chemistry better than I do; they learned it elsewhere) as well as improve my English, since I come from a non-English-speaking country. I hope the editors who remember me from more than ten years ago will say that I have at least partially succeeded in that course. Over time, I grew a genuine liking to writing and thinking about how my writing will be perceived by others. What kind of content do I want, can I provide that? I asked myself questions and looked for answers to them, that was also a major part of the experience. I liked my writing, and others did, too; that came with practice. I also got a liking for collecting bronze stars.
 * I started working on fluorine because I expected that article to be an easy target, given how its chemistry is always formation of mononegative anions. I learned along the way that the task was more difficult than I imagined (okay, I learned some chemistry here). It wasn't easy, but in the end the goal was reached. Along the way, I met User:TCO (who is, sadly, not around anymore). He had a very positive effect on me, particularly with this essay of his. It taught me to want to provide value rather than collect stickers. I've been doing that ever since.
 * So, try to understand what it is that you'd like to do. If you're anything like me, I would suggest considering starting to aim for a bronze star on a regular element (not an overly important and therefore difficult one, like sulfur or gold), even regular elements have articles with tens of thousands of views every month. It'll teach you a lot along the way. Other editors will be glad to assist a new member finding his way. You can also ask me personally, I like to think I have a lot of tips to share, and I'll be glad to help out, too, though just in case, you better communicate with me per email since I'm not around for the time being. I harbor plans to return one day, but that day is not nigh yet. I won't be bothered if you contact me often, though I can't promise to respond quickly.
 * If you're not, well, be yourself; you do you. It's not gonna be fun if you don't enjoy it.
 * Also, do contact me anyway, since I can share a bunch of sources with you, which will help you greatly to write an article (they helped me a lot). Click on my user page, and on the panel on the left you'll see an option saying something like "Email this user."--R8R (talk) 18:27, 29 May 2024 (UTC)

Nonmetal FAC #9
Is anyone able to comment on this nomination(?); there's no obligation. Thanks, Sandbh (talk) 03:43, 29 May 2024 (UTC)

 * For my fellow jargon-impaired editors:
 * FAC is wp:Featured article candidates
 * #9 is the 9th attempt at pass.
 * the article is Nonmetal
 * Johnjbarton (talk) 14:31, 29 May 2024 (UTC)

Adding some images to the superheavy elements
There are a number of superheavy elements with no macroscopic quantities, whose preview images come up as confusing diagrams of their crystal structure. So, I've decided to add some electron diagrams. I don't know if there have been discussions on this before (I couldn't find any), but I figured it was a big enough topic I'd put a notice on some talk pages. Mrfoogles (talk) 21:33, 29 June 2024 (UTC)

 * A link to the page(s) you are discussing would be helpful. Johnjbarton (talk) 22:05, 29 June 2024 (UTC)
 * I was looking at Nihonium when I thought of adding them, but essentially all the elements articles above Einsteinium (not including that one). There are a lot of them, but Copernicium, Oganesson, Flerovium, etc. Mrfoogles (talk) 00:06, 30 June 2024 (UTC)

 * This has been discussed before, but not recently: the latest thread I can find is this one from 2013.
 * I oppose adding these diagrams because they're oversimplified and misleading – good to introduce the concept to someone unfamiliar with chemistry or atomic physics, but inappropriate to illustrate a higher-level article. Namely, electrons do not "orbit" the nucleus in a classical sense, but are governed by quantum mechanics wherein wave–particle duality is significant. We never know exactly where an electron is – only where it is most likely to be, as described by its wavefunction and observed in interactions with other particles – and atomic orbitals are not orderly, concentric rings as depicted in the diagrams.
 * While it also is not necessary to explain basic quantum mechanics in every element article, it's better to have no image than a misleading image, especially since quantum mechanical effects become more significant for superheavy elements. I ask that you revert your additions on these grounds. Complex / Rational  23:46, 29 June 2024 (UTC)
 * It's true that the electrons are not physically in the positions shown on the Bohr diagram, and that they aren't actually in circular shells around the atom. But what Bohr diagrams show technically are energy levels, and that is a valid way to view an atom. I think that if there were photos of the electron density around superheavy atoms, those would be great images to use, but given that those photos don't exist (I assume, given most superheavy atoms evaporate long before they could be taken), I think this might be the best picture that can be there.
 * I don't think the image is misleading. If you look at this diagram, it's interesting to notice that not all of the electrons are in the lowest shell they could be in: 2 are in the outside shell when the second-to-outside shell is not already filled. So it actually does illustrate some complicated effects around which orbitals are the lowest energy, and it has some useful information. I think that the image isn't really misleading to people who do know about orbital shapes, because they know to treat it as an energy level diagram, and even if you did think electrons when in spherical shells around the atom, it isn't a drawing of spherical shells.
 * What I mean is it's an energy level diagram, not an orbital shape diagram. It doesn't dispel misconceptions, but I don't think it perpetuates them. I think it should be included because it has a decent amount of useful information, and it's the best image that exists currently, and it's nice to have a visual complement to an article. Also, it means the article previews aren't the confusing crystal structure diagrams anymore (which was the original motivation) Mrfoogles (talk) 00:22, 30 June 2024 (UTC)
 * But it does perpetuate a misconception. In darmstadtium, the 7s energy level is actually lower in energy than the 6d, yet it is drawn as higher. Meanwhile, for oganesson, the eight outer electrons are actually at three very different energy levels (two in 7s, two in 7p1/2, four in 7p3/2), so much so that only the four 7p3/2 electrons should be available for chemistry. The model just doesn't work that well for superheavy elements when relativity is too important to ignore.
 * I removed the diagram for Nh as well. Yes, to some extent the crystal structure images are confusing, but the issue with such elements is that no image is actually possible. I wonder if it's possible to suppress images altogether for the preview: that would be preferable, IMHO. Double sharp (talk) 06:18, 30 June 2024 (UTC)
 * Agreed that it would perpetuate a misconception, particularly for superheavy elements and still-undiscovered elements beyond (when the Aufbau principle breaks down altogether).
 * Also, it looks like is possible to suppress some images from page previews (see mw:Extension:PageImages), though because the image is called to the infobox in a nontrivial manner and the infobox is then transcluded to the article,   won't work here. I'll ask around if there's a better way than using MediaWiki:Pageimages-denylist.  Complex / Rational  02:32, 1 July 2024 (UTC)
 * Removing the ones other than Nihonium for now (thanks to a SVG bug, could only add a few anyway). Mrfoogles (talk) 00:28, 30 June 2024 (UTC)
 * A bit more context given people replied to this (surprisingly quickly): was going to add the images made by User:GregRobson, which all got turned into SVGs a while ago. Ran into the problem that a lot of the SVGs have some sort of bug where they display correctly on most software but not while minimized on Wikipedia, so I only added a few. (Think it can get fixed by running them through a minifier or formatter, but could not figure out how to reupload images to Commons). Leaving Nihonium up for an example to look at. Mrfoogles (talk) 00:39, 30 June 2024 (UTC)
 * Update: Can't really disagree with what @Double sharp said, and mostly the people here seem to not like this idea, so I'm giving this one up. No idea if there's any way to disable previews on Wikipedia, but I think probably not. Mrfoogles (talk) 18:10, 30 June 2024 (UTC)
 * I removed the crystal structure images from the page previews. Thanks for technical assistance.  Complex / Rational  12:57, 3 July 2024 (UTC)

Isotopes of argon
Upon updating Isotopes of argon, I noticed that a reference used for the lightest isotope, 29Ar, does not quote a half-life or decay-width measurement for this nucleus — I do not see how the value of 40 zs (decay width 11 keV) was obtained. However, the lower bound reported in NUBASE2020 is implausibly large compared to the upper bound reported for 30Ar. This also affects 28Cl, which was discovered in the same paper. –LaundryPizza03 ( d c̄ ) 05:54, 2 July 2024 (UTC)

 * Huh. Looks like I added it in 2019, probably making a calculation mistake when invoking WP:CALC. It's probably better to not write anything in the table, though, since such an unbound state would have a lifetime many orders of magnitude shorter than the NUBASE2020 lower bound. Thanks for taking note of this. Complex / Rational  14:03, 2 July 2024 (UTC)
 * 5.5 MeV is a decay energy, not a decay width. –LaundryPizza03 ( d c̄ ) 15:07, 2 July 2024 (UTC)
 * IT notes regarding:
 * The full width at half maximum of the probability distribution provides the evaluation of the [proton-emission decay energy] uncertainty.
 * For the lowest observed state of 29Ar, this is reported as 0.18 MeV, or 2.5 zs — the ground state is postulated to lie at a lower level. For 28Cl, this is 0.08 MeV (6 zs). –LaundryPizza03 ( d c̄ ) 18:29, 2 July 2024 (UTC)
 * Never mind, this is something different. –LaundryPizza03 ( d c̄ ) 18:58, 2 July 2024 (UTC)
 * Would you like to update the elements Fm–Og to NUBASE2020 where applicable? This is complicated by the heavy reliance on other sources. –LaundryPizza03 ( d c̄ ) 19:05, 2 July 2024 (UTC)
 * I think a good rule of thumb for those is to use NUBASE2020 if the most recent data predates 2020, and cite individual articles for nuclides investigated in subsequent studies. I can start reviewing the lists from Og and work my way down. Complex / Rational  11:44, 3 July 2024 (UTC)

Conflicting images of noble gases
I added an image to Deuterium a while ago when I found one, and I recently noticed there was already an image for it on the Hydrogen page. The problem is that while, by @Alchemist-hp, glows pink, , by this website, glows purplish-white. Does anyone know which of these are correct? I think image two is preferable because it highlights the color of the gas more, but I'm starting to wonder if the images on that website are wrong. They also disagree on helium: see and. Helium has a particularly stark difference: maybe it's that different energy transitions are active or something related to that? The sites and the alchemist-hp images agree on Argon, Xenon, and Krypton fairly well, too. Mrfoogles (talk) 21:09, 2 July 2024 (UTC)
 * I would go with Alchemist-hp's images. Per this 2011 discussion, the other set may have purity concerns. Double sharp (talk) 04:35, 3 July 2024 (UTC)
 * Thanks, that's pretty much what I was looking for. Disappointing, though: the other set was pretty nice for highlighting the color (the alchemist-hp ones had different colors in different parts of the displayed tube, which I think subtracted from the effect a bit). I'll remove the deuterium one.
 * The Argon, Xenon, and Krypton ones possibly are uncontaminated, but it might be better not to use them. Maybe it would be better to crop the alchemist-hp images? Mrfoogles (talk) 04:57, 3 July 2024 (UTC)
 * Update: did that Mrfoogles (talk) 05:32, 3 July 2024 (UTC)
 * Cool! Double sharp (talk) 06:27, 3 July 2024 (UTC)

Template:NUBASE2020
The article on Erbium the section on Isotopes uses NUBASE2020 as its sole reference. Then it makes statements like: However, the NUBASE reference contains nothing but tables of isotope properties. It seems to me that we could cite the table for facts about specific isotopes, but nothing about the collection of them. That is, the entire isotopes section is original research based on analyzing the tables. Since this is a template reference it seem like the use may be widespread. What do you think? Johnjbarton (talk) 16:21, 9 July 2024 (UTC)
 * Naturally occurring erbium is composed of 6 stable isotopes...

 * NUBASE includes detailed decay data, and for primordial isotopes, gives their fraction of natural abundance. Indeed it is widely used as a reference, though in exactly the same context (citing isotope data), and pages that contain data more recent than 2020 or describe applications or properties in detail have additional reference. I wouldn't say that identifying precisely six primordial (and stable, as it happens) erbium isotopes from the table, given that they have abundance fractions, is WP:OR; arguably it's simple counting as permitted under WP:CALC. However, if you feel that adding additional sources would be helpful, feel free to do so. Complex / Rational  17:40, 9 July 2024 (UTC)

Cropping gas discharge tube images
I cropped a few of the gas discharge tube images to make it more clear which part was the noble gas (specifically krypton, argon, and xenon are currently cropped) but this has been contested by @Zzzs (pinging here), so I'm putting up a talk page section.

 * Why I cropped the images: With the strong colors from both parts of the tube it's hard to tell which part is the gas; cropping it makes it obvious and makes it easier to compare them. It also makes the images less overly wide, which is good generally. Mostly it makes the image dominated by the important color. I reverted hydrogen because that one doesn't have very strong colors not coming from the gas, so it doesn't really need it, but I think the other ones do.

They are featured pictures, but it's still a featured picture if you crop to the important bit for ease of understanding & comparison. Mrfoogles (talk) 18:49, 19 July 2024 (UTC)

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Wikipedia talk:WikiProject Elements