Beryllium,  4Be
Pronunciationm/ (RIL-ee-əm)
Appearancewhite-gray metallic
Standard atomic weight Ar, std(Be)9.0121831(5)[1]
Beryllium in the periodic table
CaesiumBariumLanthanumCeriumPraseodymiumNeodymiumPromethiumSamariumEuropiumGadoliniumTerbiumDysprosiumHolmiumErbiumThuliumYtterbiumLutetiumHafniumTantalumTungstenRheniumOsmiumIridiumPlatinumGoldMercury (element)ThalliumLeadBismuthPoloniumAstatineRadon


Atomic number (Z)4
Groupgroup 2 (alkaline earth metals)
Periodperiod 2
Element category  alkaline earth metal
Electron configuration[He] 2s2
Electrons per shell
2, 2
Physical properties
Phase at STPsolid
Melting point1560 K ​(1287 °C, ​2349 °F)
Boiling point2742 K ​(2469 °C, ​4476 °F)
Density (near r.t.)1.85 g/cm3
when liquid (at m.p.)1.690 g/cm3
Critical point5205 K,  MPa (extrapolated)
Heat of fusion12.2 kJ/mol
Heat of vaporization292 kJ/mol
Molar heat capacity16.443 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)146216081791202323272742
Atomic properties
Oxidation states+1,[2] +2 (an amphoteric oxide)
ElectronegativityPauling scale: 1.57
Ionization energies
  • 1st: 899.5 kJ/mol
  • 2nd: 1757.1 kJ/mol
  • 3rd: 14,848.7 kJ/mol
  • (more)
Atomic radiusempirical: 112 pm
Covalent radius96±3 pm
Van der Waals radius153 pm
Color lines in a spectral range
Spectral lines of beryllium
Other properties
Natural occurrenceprimordial
Crystal structurehexagonal close-packed (hcp)
Hexagonal close packed crystal structure for beryllium
Speed of sound thin rod12,890 m/s (at r.t.)[3]
Thermal expansion11.3 µm/(m·K) (at 25 °C)
Thermal conductivity200 W/(m·K)
Electrical resistivity36 nΩ·m (at 20 °C)
Magnetic orderingdiamagnetic
Magnetic susceptibility−9.0·10−6 cm3/mol[4]
Young's modulus287 GPa
Shear modulus132 GPa
Bulk modulus130 GPa
Poisson ratio0.032
Mohs hardness5.5
Vickers hardness1670 MPa
Brinell hardness590–1320 MPa
CAS Number7440-41-7
DiscoveryLouis Nicolas Vauquelin (1798)
First isolationFriedrich Wöhler & Antoine Bussy (1828)
Main isotopes of beryllium
Iso­topeAbun­danceHalf-life (t1/2)Decay modePro­duct
7Betrace53.12 dε7Li
10Betrace1.39×106 yβ10B
| references

Beryllium is a chemical element with the symbol Be and atomic number 4. 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. 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.

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.[6] 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.[6] The high thermal conductivities of beryllium and beryllium oxide have led to their use in thermal management applications. When added as an alloying element to aluminium, copper (notably the alloy beryllium copper), iron or nickel beryllium improves many physical properties.[example needed][6] Tools made of beryllium copper alloys are strong and hard and do not create sparks when they strike a steel surface. Beryllium does not form oxides until it reaches very high temperatures.

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.[7]


Physical properties

Beryllium is a steel gray and hard metal that is brittle at room temperature and has a close-packed hexagonal crystal structure.[6] It has exceptional stiffness (Young's modulus 287 GPa) and a melting point of 1287 C. 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.[8]

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 – 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:[9]

+ n → 2 4
+ 2 n

Neutrons are liberated when beryllium nuclei are struck by energetic alpha particles[8] producing the nuclear reaction

+ 4
+ n

where 4
is an alpha particle and 12
is a carbon-12 nucleus.[9] 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
+ 6
,    6
+ β,    6
+ n → 4
+ 3

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.[10]

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

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.[11] 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.[12] 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.[13] 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.[12] 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.[14] 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 7×1017 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.[15] 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.[16]

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.[17]

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.[18] The exotic isotopes 11Be and 14Be are known to exhibit a nuclear halo.[19] 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 compound of beryllium.

The Sun has a concentration of 0.1 parts per billion (ppb) of beryllium.[20] Beryllium has a concentration of 2 to 6 parts per million (ppm) in the Earth's crust.[21] It is most concentrated in the soils, 6 ppm.[22] Trace amounts of 9Be are found in the Earth's atmosphere.[22] The concentration of beryllium in sea water is 0.2–0.6 parts per trillion.[22][23] In stream water, however, beryllium is more abundant with a concentration of 0.1 ppb.[24]

Beryllium is found in over 100 minerals,[25] 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.[8][26][27] The green color in gem-quality forms of beryl comes from varying amounts of chromium (about 2% for emerald).[28]

The two main ores of beryllium, beryl and bertrandite, are found in Argentina, Brazil, India, Madagascar, Russia and the United States.[28] Total world reserves of beryllium ore are greater than 400,000 tonnes.[28]

Other Languages
Afrikaans: Berillium
አማርኛ: ቤሪሊየም
العربية: بيريليوم
aragonés: Berilio
armãneashti: Beriliu
asturianu: Beriliu
azərbaycanca: Berillium
تۆرکجه: بریلیوم
Bân-lâm-gú: Beryllium
беларуская: Берылій
беларуская (тарашкевіца)‎: Бэрыль (элемэнт)
भोजपुरी: बेरिलियम
български: Берилий
བོད་ཡིག: བེ་རི་ལིམ།
bosanski: Berilij
brezhoneg: Beriliom
català: Beril·li
Чӑвашла: Берилли
Cebuano: Berilio
čeština: Beryllium
chiShona: Beryllium
corsu: Berilliu
Cymraeg: Beriliwm
dansk: Beryllium
Deutsch: Beryllium
eesti: Berüllium
Ελληνικά: Βηρύλλιο
emiliàn e rumagnòl: Berìli
español: Berilio
Esperanto: Berilio
euskara: Berilio
فارسی: بریلیم
Fiji Hindi: Beryllium
føroyskt: Beryllium
français: Béryllium
Frysk: Beryllium
furlan: Berili
Gaeilge: Beirilliam
Gaelg: Beryllium
Gàidhlig: Beirilium
galego: Berilio
Gĩkũyũ: Beryllium
ગુજરાતી: બેરિલિયમ
客家語/Hak-kâ-ngî: Beryllium
хальмг: Белүр
한국어: 베릴륨
Hawaiʻi: Beryllium
հայերեն: Բերիլիում
हिन्दी: बेरिलियम
hornjoserbsce: Berylium
hrvatski: Berilij
Ido: Berilio
Bahasa Indonesia: Berilium
interlingua: Beryllium
íslenska: Beryllín
italiano: Berillio
עברית: בריליום
Kabɩyɛ: Bɛrɩlɩyɔm
ქართული: ბერილიუმი
қазақша: Бериллий
Kiswahili: Berili
Kreyòl ayisyen: Berilyòm
kurdî: Berîlyûm
Кыргызча: Бериллий
кырык мары: Бериллий
Latina: Beryllium
latviešu: Berilijs
Lëtzebuergesch: Beryllium
lietuvių: Berilis
Ligure: Berillio
Limburgs: Beryl
lingála: Belilu
Livvinkarjala: Berillium
la .lojban.: jinmrberilo
lumbaart: Berilio
magyar: Berillium
македонски: Берилиум
മലയാളം: ബെറിലിയം
Māori: Konuuku
मराठी: बेरिलियम
Bahasa Melayu: Berilium
Mìng-dĕ̤ng-ngṳ̄: Pì (gĭng-sṳ̆k)
монгол: Берилли
မြန်မာဘာသာ: ဘယ်ရီလီယမ်
Nederlands: Beryllium
नेपाली: बेरिलियम
नेपाल भाषा: बेरिलियम
日本語: ベリリウム
Nordfriisk: Beryllium
norsk: Beryllium
norsk nynorsk: Beryllium
occitan: Berilli
ଓଡ଼ିଆ: ବେରିଲିୟମ
oʻzbekcha/ўзбекча: Berilliy
ਪੰਜਾਬੀ: ਬੇਰਿਲੀਅਮ
پنجابی: بیریلیم
Papiamentu: Beryllio
ភាសាខ្មែរ: បេរីល្យូម
Piemontèis: Berili
Plattdüütsch: Beryllium
português: Berílio
română: Beriliu
Runa Simi: Berilyu
русский: Бериллий
саха тыла: Бериллиум
संस्कृतम्: बेरिलियम्
Scots: Beryllium
Seeltersk: Beryllium
shqip: Beriliumi
sicilianu: Birìlliu
Simple English: Beryllium
slovenčina: Berýlium
slovenščina: Berilij
Soomaaliga: Beriiliyaam
کوردی: بێریلیۆم
српски / srpski: Берилијум
srpskohrvatski / српскохрватски: Berilijum
Basa Sunda: Bérilium
suomi: Beryllium
svenska: Beryllium
Tagalog: Berilyo
татарча/tatarça: Бериллий
తెలుగు: బెరీలియం
тоҷикӣ: Бериллий
Türkçe: Berilyum
українська: Берилій
اردو: بیریلیم
ئۇيغۇرچە / Uyghurche: بېرىللىي
vepsän kel’: Berillii
Tiếng Việt: Berili
Winaray: Berilyo
ייִדיש: בעריליום