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Beryllium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements


                 4               lithium ← beryllium → boron
                 -
                ↑
                Be
                ↓
                Mg

                                  Periodic Table - Extended Periodic Table

                                                                   General
                                     Name, Symbol, Number beryllium, Be, 4
                                     Chemical series alkaline earth metals
                                              Group, Period, Block 2, 2, s
                                            Appearance white-gray metallic
                                            Atomic mass 9.012182 (3) g/mol
                                          Electron configuration 1s^2 2s^2
                                                  Electrons per shell 2, 2
                                                       Physical properties
                                                               Phase solid
                                       Density (near r.t.) 1.85 g·cm^−3
                                   Liquid density at m.p. 1.690 g·cm^−3
                                                     Melting point 1560  K
                                                    (1287 ° C, 2349 ° F)
                                                      Boiling point 2742 K
                                                    (2469 ° C, 4476 ° F)
                                         Heat of fusion 7.895 kJ·mol^−1
                                     Heat of vaporization 297 kJ·mol^−1
                         Heat capacity (25 °C) 16.443 J·mol^−1·K^−1

   CAPTION: Vapor pressure

                                      P/Pa   1    10  100  1 k  10 k 100 k
                                     at T/K 1462 1608 1791 2023 2327 2742

                                                         Atomic properties
                                               Crystal structure hexagonal
                                                        Oxidation states 2
                                                       ( amphoteric oxide)
                                    Electronegativity 1.57 (Pauling scale)
                                                       Ionization energies
                                           ( more) 1st: 899.5 kJ·mol^−1
                                                  2nd: 1757.1 kJ·mol^−1
                                                 3rd: 14848.7 kJ·mol^−1
                                                      Atomic radius 105 pm
                                              Atomic radius (calc.) 112 pm
                                                     Covalent radius 90 pm
                                                             Miscellaneous
                                             Magnetic ordering diamagnetic
                               Electrical resistivity (20 °C) 35.6 nΩ·m
                        Thermal conductivity (300 K) 200 W·m^−1·K^−1
                       Thermal expansion (25 °C) 11.3 µm·m^−1·K^−1
                       Speed of sound (thin rod) ( r.t.) 12870   m·s^−1
                                                   Young's modulus 287 GPa
                                                     Shear modulus 132 GPa
                                                      Bulk modulus 130 GPa
                                                       Poisson ratio 0.032
                                                         Mohs hardness 5.5
                                                 Vickers hardness 1670 MPa
                                                  Brinell hardness 600 MPa
                                             CAS registry number 7440-41-7
                                                         Selected isotopes

                CAPTION: Main article: Isotopes of beryllium

                                 iso   NA    half-life  DM  DE ( MeV)  DP
                                ^7Be  syn   53.12 d     ε   -         ^7Li
                                                        γ   0.477     -
                                ^9Be  100%  Be is stable with 5 neutrons
                                ^10Be trace 1.51×10^6 y β^- 0.556     ^10B

                                                                References

   Beryllium ( IPA: /bəˈrɪliəm/) is the chemical element in the periodic
   table that has the symbol Be and atomic number 4. A bivalent element,
   beryllium is a steel grey, strong, light-weight yet brittle, alkaline
   earth metal, that is primarily used as a hardening agent in alloys
   (most notably beryllium copper).

Notable characteristics

   Beryllium has one of the highest melting points of the light metals.
   The modulus of elasticity of beryllium is approximately ^1/[3] greater
   than that of steel. It has excellent thermal conductivity, is
   nonmagnetic and resists attack by concentrated nitric acid. It is
   highly permeable to X-rays, and neutrons are liberated when it is hit
   by alpha particles, as from radium or polonium (about 30
   neutrons/million alpha particles). At standard temperature and
   pressures beryllium resists oxidation when exposed to air (although its
   ability to scratch glass is probably due to the formation of a thin
   layer of the oxide). The speed of sound in beryllium (12,500m/s) is
   greater than in any other element.

History

   The name beryllium comes from the Greek beryllos, beryl, from Prakrit
   veruliya, from Pāli veuriya; possibly from or simply akin to a
   Dravidian source represented by Tamil veiruor, viar, "to whiten, become
   pale." At one time beryllium was referred to as glucinium (from Greek
   glykys, sweet), due to the sweet taste of its salts. This element was
   discovered by Louis Vauquelin in 1798 as the oxide in beryl and in
   emeralds. Friedrich Wöhler and A. A. Bussy independently isolated the
   metal in 1828 by reacting potassium and beryllium chloride.

Occurrence

   Beryllium is an essential constituent of about 100 out of about 4000
   known minerals, the most important of which are bertrandite
   (Be[4]Si[2]O[7](OH)[2]), beryl (Al[2]Be[3]Si[6]O[18]), chrysoberyl
   (Al[2]BeO[4]), and phenakite (Be[2]SiO[4]). Precious forms of beryl are
   aquamarine and emerald.

   The most important commercial sources of beryllium and its compounds
   are beryl and bertrandite. Beryllium metal did not become readily
   available until 1957. Currently, most production of this metal is
   accomplished by reducing beryllium fluoride with magnesium metal. The
   price on the US market for vacuum-cast beryllium ingots was 338 US$ per
   pound ($745/kg) in 2001.

          BeF[2] + Mg → MgF[2] + Be

Applications

     * Beryllium is used as an alloying agent in the production of
       beryllium-copper because of its ability to absorb large amounts of
       heat. Beryllium-copper alloys are used in a wide variety of
       applications because of their electrical and thermal conductivity,
       high strength and hardness, nonmagnetic properties, along with good
       corrosion and fatigue resistance. These applications include the
       making of spot-welding electrodes, springs, non-sparking tools and
       electrical contacts.
     * Due to their stiffness, light weight, and dimensional stability
       over a wide temperature range, beryllium-copper alloys are also
       used in the defense and aerospace industries as light-weight
       structural materials in high-speed aircraft, missiles, space
       vehicles and communication satellites.
     * Thin sheets of beryllium foil are used with X-ray detection
       diagnostics to filter out visible light and allow only X-rays to be
       detected.
     * Beryllium is an effective 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).
     * In the field of X-ray lithography beryllium is used for the
       reproduction of microscopic integrated circuits.
     * In the telecommunications industry, Beryllium is made into tools
       that are used to tune the highly magnetic klystrons used for high
       power microwave transmissions for safety.
     * Because it has a low thermal neutron absorption cross section, the
       nuclear power industry uses this metal in nuclear reactors as a
       neutron reflector and moderator.
     * Beryllium is used in nuclear weapons for similar reasons. For
       example, the critical mass of a plutonium sphere is significantly
       reduced if the plutonium is surrounded by a beryllium shell.
     * Beryllium is sometimes used in neutron sources, in which the
       beryllium is mixed with an alpha emitter such as ^210Po, ^226Ra,
       ^239Pu or ^241Am.
     * Beryllium is also used in the making of gyroscopes, various
       computer equipment, watch springs and instruments where
       light-weight, rigidity and dimensional stability are needed.
     * Beryllium oxide is useful for many applications that require an
       excellent heat conductor, with high strength and hardness, with a
       very high melting point, and that acts as an electrical insulator.
     * Beryllium compounds were once used in fluorescent lighting tubes,
       but this use was discontinued because of berylliosis in the workers
       manufacturing the tubes (see below).
     * The James Webb Space Telescope will have 18 hexagonal beryllium
       sections for its mirrors. Because JWST will face a temperature of
       −240 degrees Celsius (30 kelvins), the mirror is made of beryllium,
       a material capable of handling extreme cold better than glass.
       Beryllium contracts and deforms less than glass — and thus remains
       more uniform — in such temperatures. For the same reason, the
       optics of the Spitzer Space Telescope are entirely built of
       beryllium.
     * Beryllium is also used in the Joint European Torus fusion research
       facility, to condition the plasma facing components.
     * Beryllium has also been used in tweeter construction by the company
       Focal-JMlab on its flagship Utopia Be series as an alternative to
       titanium and aluminium, largely due to its lower density and
       greater rigidity.

Isotopes

   Plot showing variations in solar activity, including variation in 10Be
   concentration.
   Enlarge
   Plot showing variations in solar activity, including variation in ^10Be
   concentration.

   Of beryllium's isotopes, only ^9Be is stable. Cosmogenic ^10Be is
   produced in the atmosphere by cosmic ray spallation of oxygen and
   nitrogen. Because beryllium tends to exist in solution at pH levels
   less than about 5.5 (and most rainwater has a pH less than 5), it will
   enter into solution and be transported to the Earth's surface via
   rainwater. As the precipitation quickly becomes more alkaline,
   beryllium drops out of solution. Cosmogenic ^10Be thereby accumulates
   at the soil surface, where its relatively long half-life (1.51 million
   years) permits a long residence time before decaying to ^10B. ^10Be and
   its daughter products have been used to examine soil erosion, soil
   formation from regolith, the development of lateritic soils, as well as
   variations in solar activity and the age of ice cores.

   The fact that ^7Be and ^8Be are unstable has profound cosmological
   consequences as it means that elements heavier than beryllium could not
   be produced by nuclear fusion in the Big Bang. Moreover, the nuclear
   energy levels of ^8Be are such that carbon can be produced within
   stars, thus making life possible. (See triple-alpha process and Big
   Bang nucleosynthesis).

   The shortest-lived known isotope of beryllium is ^13Be which decays
   through neutron emission. It has a half-life of 2.7 × 10^-21 seconds.
   ^6Be also is also very short-lived with a half-life of 5.0 × 10^-21
   seconds.

   The exotics ^11Be and ^14Be are known to exhibit a nuclear halo.

Health effects

Precautions

   Beryllium ore
   Enlarge
   Beryllium ore

   Beryllium and its salts are toxic substances and potentially
   carcinogenic. Chronic berylliosis is a pulmonary and systemic
   granulomatous disease caused by exposure to beryllium. Acute beryllium
   disease in the form of chemical pneumonitis was first reported in
   Europe in 1933 and in the United States in 1943. Cases of chronic
   berylliosis were first described in 1946 among workers in plants
   manufacturing fluorescent lamps in Massachusetts. Chronic berylliosis
   resembles sarcoidosis in many respects, and the differential diagnosis
   is often difficult.

   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 and in the refining of beryllium
   metal and melting of beryllium-containing alloys, the manufacturing of
   electronic devices, and the handling of other beryllium-containing
   material.

   Early researchers tasted beryllium and its various compounds for
   sweetness in order to verify its presence. Modern diagnostic equipment
   no longer necessitates this highly risky procedure and no attempt
   should be made to ingest this substance. Beryllium and its compounds
   should be handled with great care and special precautions must be taken
   when carrying out any activity which could result in the release of
   beryllium dust (lung cancer is a possible result of prolonged exposure
   to beryllium laden dust).

   This substance can be handled safely if certain procedures are
   followed. No attempt should be made to work with beryllium before
   familiarization with correct handling procedures.

   A successful test for beryllium on different surface areas has been
   recently developed. The procedure uses fluorescence when beryllium is
   bound to sulfonated hydroxybenzoquinoline to detect up to 10 times
   lower than the recommended limit for beryllium concentration in the
   work place. Fluorescence increases with increasing beryllium
   concentration. The new procedure has been successfully tested on a
   variety of surfaces.

Inhalation

   Beryllium can be harmful if inhaled and the effects depend on period of
   exposure. If beryllium air levels are high enough (greater than 100
   µg/m³), an acute condition can result, called acute beryllium disease,
   which resembles pneumonia. Occupational and community air standards are
   effective in preventing most acute lung damage. Long term exposure to
   beryllium can increase the risk of developing lung cancer. The more
   common and serious health hazard from beryllium today is chronic
   beryllium disease (CBD), discussed below. It continues to occur in
   industries as diverse as metal recycling, dental laboratories, alloy
   manufacturing, nuclear weapons production, defense industries, and
   metal machine shops that work with alloys containing small amounts of
   beryllium.
   A square beryllium foil mounted in a steel case to be used as a window
   between a vacuum chamber and an X-ray microscope. Beryllium, due to its
   low Z number is highly transparent to X-rays.
   Enlarge
   A square beryllium foil mounted in a steel case to be used as a window
   between a vacuum chamber and an X-ray microscope. Beryllium, due to its
   low Z number is highly transparent to X-rays.

Chronic beryllium disease (CBD)

   Some people (1-15%) become sensitive to beryllium. These individuals
   may develop an inflammatory reaction that principally targets the
   respiratory system and skin. This condition is called chronic beryllium
   disease (CBD), and can occur within a few months or many years after
   exposure to higher than normal levels of beryllium (greater than 0.02
   µg/m³). This disease causes fatigue, weakness, night sweats and can
   cause difficulty in breathing and a persistent dry cough. It can result
   in anorexia, weight loss, and may also lead to right-side heart
   enlargement and heart disease in advanced cases. Some people who are
   sensitized to beryllium may not have any symptoms. The disease is
   treatable but not curable. CBD occurs when the body's immune system
   recognizes beryllium particles as foreign material and mounts an immune
   system attack against the particles. Because these particles are
   typically inhaled into the lungs, the lungs becomes the major site
   where the immune system responds. The lungs become inflamed, filled
   with large numbers of white blood cells that accumulate wherever
   beryllium particles are found. The cells form balls around the
   beryllium particles called "granulomas." When enough of these
   granulomas develop, they interfere with the normal function of the
   organ. Over time, the lungs become stiff and lose their ability to help
   transfer oxygen from the air into the bloodstream. Patients with CBD
   develop difficulty inhaling and exhaling sufficient amounts of air and
   the amount of oxygen in their bloodstreams falls. Treatment of such
   patients includes use of oxygen and medicines that try to suppress the
   immune system's over-reaction to beryllium. A class of
   immunosuppressive medicines called glucocorticoids (example:
   prednisone), is most commonly used as treatment. The general population
   is unlikely to develop acute or chronic beryllium disease because
   ambient air levels of beryllium are normally very low (0.00003-0.0002
   µg/m³).

Ingestion

   Swallowing beryllium has not been reported to cause effects in humans
   because very little beryllium is absorbed from the stomach and
   intestines. Ulcers have been seen in dogs ingesting beryllium in the
   diet. Beryllium contact with skin that has been scraped or cut may
   cause rashes or ulcers, or bumps under the skin called "granulomas."

Effects on children

   There are no studies on the health effects of children exposed to
   beryllium, although individual cases of CBD have been reported in
   children of beryllium workers from the 1940s. It is likely that the
   health effects seen in children exposed to beryllium will be similar to
   the effects seen in adults. It is unknown whether children differ from
   adults in their susceptibility to beryllium. It is unclear whether
   beryllium is teratogenic.

Detection in the body

   Beryllium can be measured in the urine and blood. The amount of
   beryllium in blood or urine may not indicate time or quantity of
   exposure. Beryllium levels can also be measured in lung and skin
   samples. While such measurements may help establish that exposure has
   occurred, other tests are used to determine if that exposure has
   resulted in health effects. A blood test, the blood beryllium
   lymphocyte proliferation test (BeLPT), identifies beryllium
   sensitization and has predictive value for CBD. The BeLPT has become
   the standard test for detecting beryllium sensitization and CBD in
   individuals who are suspected of having CBD and to help distinguish it
   from similar conditions such as sarcoidosis. It is also the main test
   used in industry health programs to monitor whether disease is
   occurring among current and former workers who have been exposed to
   beryllium on the job. The test can detect disease that is at an early
   stage, or can detect disease at more advanced stages of illness as
   well. The BeLPT can also be performed using cells obtained from a
   person's lung by a procedure called "bronchoscopy."

Industrial release limits

   Typical levels of beryllium that industries may release into the air
   are of the order of 0.01 µg/m³, averaged over a 30-day period, or 2
   µg/m³ of workroom air for an 8-hour work shift. Compliance with the
   current U.S. Occupational Safety and Health Administration (OSHA)
   permissible exposure limit for beryllium of 2 µg/m³ has been determined
   to be inadequate to protect workers from developing beryllium
   sensitization and CBD. The American Conference of Governmental
   Industrial Hygienists (ACGIH), which is an independent organization of
   experts in the field of occupational health, has proposed a threshold
   limit value (TLV) of 0.05 µg/m³ in a 2006 Notice of Intended Change
   (NIC). This TLV is 40 times lower than the current OHSA permissible
   exposure limit, reflecting the ACGIH analysis of best available
   peer-reviewed research data concerning how little airborne beryllium is
   required to cause sensitization and CBD. Because it can be difficult to
   control industrial exposures to beryllium, it is advisable to use any
   methods possible to reduce airborne and surface contamination by
   beryllium, to minimize the use of beryllium and beryllium-containing
   alloys whenever possible, and to educate people about the potential
   hazards if they are likely to encounter beryllium dust or fumes.

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