Boron

  • boron, 5b
    boron r105.jpg
    boron (β-rhombohedral)[1]
    boron
    pronunciationn/ (bor-on)
    allotropesα-, β-rhombohedral, β-tetragonal (and more)
    appearanceblack-brown
    standard atomic weight ar, std(b)[10.80610.821] conventional: 10.81
    boron in the periodic table
    hydrogen helium
    lithium beryllium boron carbon nitrogen oxygen fluorine neon
    sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
    potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
    rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
    caesium barium lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury (element) thallium lead bismuth polonium astatine radon
    francium radium actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson


    b

    al
    berylliumboroncarbon
    atomic number (z)5
    groupgroup 13 (boron group)
    periodperiod 2
    blockp-block
    element category  metalloid
    electron configuration[he] 2s2 2p1
    electrons per shell2, 3
    physical properties
    phase at stpsolid
    melting point2349 k ​(2076 °c, ​3769 °f)
    boiling point4200 k ​(3927 °c, ​7101 °f)
    density when liquid (at m.p.)2.08 g/cm3
    heat of fusion50.2 kj/mol
    heat of vaporization508 kj/mol
    molar heat capacity11.087 j/(mol·k)
    vapor pressure
    p (pa) 1 10 100 1 k 10 k 100 k
    at t (k) 2348 2562 2822 3141 3545 4072
    atomic properties
    oxidation states−5, −1, 0,[2] +1, +2, +3[3][4] (a mildly acidic oxide)
    electronegativitypauling scale: 2.04
    ionization energies
    • 1st: 800.6 kj/mol
    • 2nd: 2427.1 kj/mol
    • 3rd: 3659.7 kj/mol
    • (more)
    atomic radiusempirical: 90 pm
    covalent radius84±3 pm
    van der waals radius192 pm
    color lines in a spectral range
    spectral lines of boron
    other properties
    natural occurrenceprimordial
    crystal structurerhombohedral
    rhombohedral crystal structure for boron
    speed of sound thin rod16,200 m/s (at 20 °c)
    thermal expansionβ form: 5–7 µm/(m·k) (at 25 °c)[5]
    thermal conductivity27.4 w/(m·k)
    electrical resistivity~106 Ω·m (at 20 °c)
    magnetic orderingdiamagnetic[6]
    magnetic susceptibility−6.7·10−6 cm3/mol[6]
    mohs hardness~9.5
    cas number7440-42-8
    history
    discoveryjoseph louis gay-lussac and louis jacques thénard[7] (30 june 1808)
    first isolationhumphry davy[8] (9 july 1808)
    main isotopes of boron
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    10b 20% stable[9]
    11b 80% stable[9]
    10b content is 19.1–20.3% in natural samples, with the remainder being 11b.[10]
    category category: boron
    | references

    boron is a chemical element with the symbol b and atomic number 5. produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in the solar system and in the earth's crust.[11] boron is concentrated on earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. these are mined industrially as evaporites, such as borax and kernite. the largest known boron deposits are in turkey, the largest producer of boron minerals.

    elemental boron is a metalloid that is found in small amounts in meteoroids but chemically uncombined boron is not otherwise found naturally on earth. industrially, very pure boron is produced with difficulty because of refractory contamination by carbon or other elements. several allotropes of boron exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard (about 9.5 on the mohs scale), and a poor electrical conductor at room temperature. the primary use of elemental boron is as boron filaments with applications similar to carbon fibers in some high-strength materials.

    boron is primarily used in chemical compounds. about half of all boron consumed globally is an additive in fiberglass for insulation and structural materials. the next leading use is in polymers and ceramics in high-strength, lightweight structural and refractory materials. borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. boron as sodium perborate is used as a bleach. a small amount of boron is used as a dopant in semiconductors, and reagent intermediates in the synthesis of organic fine chemicals. a few boron-containing organic pharmaceuticals are used or are in study. natural boron is composed of two stable isotopes, one of which (boron-10) has a number of uses as a neutron-capturing agent.

    in biology, borates have low toxicity in mammals (similar to table salt), but are more toxic to arthropods and are used as insecticides. boric acid is mildly antimicrobial, and several natural boron-containing organic antibiotics are known.[12] boron is an essential plant nutrient and boron compounds such as borax and boric acid are used as fertilizers in agriculture, although it's only required in small amounts, with excess being toxic. boron compounds play a strengthening role in the cell walls of all plants. there is no consensus on whether boron is an essential nutrient for mammals, including humans, although there is some evidence it supports bone health.

  • history
  • preparation of elemental boron in the laboratory
  • characteristics
  • production
  • applications
  • biological role
  • see also
  • references
  • external links

Boron, 5B
Boron R105.jpg
boron (β-rhombohedral)[1]
Boron
Pronunciationn/ (BOR-on)
Allotropesα-, β-rhombohedral, β-tetragonal (and more)
Appearanceblack-brown
Standard atomic weight Ar, std(B)[10.80610.821] conventional: 10.81
Boron in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


B

Al
berylliumboroncarbon
Atomic number (Z)5
Groupgroup 13 (boron group)
Periodperiod 2
Blockp-block
Element category  Metalloid
Electron configuration[He] 2s2 2p1
Electrons per shell2, 3
Physical properties
Phase at STPsolid
Melting point2349 K ​(2076 °C, ​3769 °F)
Boiling point4200 K ​(3927 °C, ​7101 °F)
Density when liquid (at m.p.)2.08 g/cm3
Heat of fusion50.2 kJ/mol
Heat of vaporization508 kJ/mol
Molar heat capacity11.087 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 2348 2562 2822 3141 3545 4072
Atomic properties
Oxidation states−5, −1, 0,[2] +1, +2, +3[3][4] (a mildly acidic oxide)
ElectronegativityPauling scale: 2.04
Ionization energies
  • 1st: 800.6 kJ/mol
  • 2nd: 2427.1 kJ/mol
  • 3rd: 3659.7 kJ/mol
  • (more)
Atomic radiusempirical: 90 pm
Covalent radius84±3 pm
Van der Waals radius192 pm
Color lines in a spectral range
Spectral lines of boron
Other properties
Natural occurrenceprimordial
Crystal structurerhombohedral
Rhombohedral crystal structure for boron
Speed of sound thin rod16,200 m/s (at 20 °C)
Thermal expansionβ form: 5–7 µm/(m·K) (at 25 °C)[5]
Thermal conductivity27.4 W/(m·K)
Electrical resistivity~106 Ω·m (at 20 °C)
Magnetic orderingdiamagnetic[6]
Magnetic susceptibility−6.7·10−6 cm3/mol[6]
Mohs hardness~9.5
CAS Number7440-42-8
History
DiscoveryJoseph Louis Gay-Lussac and Louis Jacques Thénard[7] (30 June 1808)
First isolationHumphry Davy[8] (9 July 1808)
Main isotopes of boron
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
10B 20% stable[9]
11B 80% stable[9]
10B content is 19.1–20.3% in natural samples, with the remainder being 11B.[10]
Category Category: Boron
| references

Boron is a chemical element with the symbol B and atomic number 5. Produced entirely by cosmic ray spallation and supernovae and not by stellar nucleosynthesis, it is a low-abundance element in the Solar system and in the Earth's crust.[11] Boron is concentrated on Earth by the water-solubility of its more common naturally occurring compounds, the borate minerals. These are mined industrially as evaporites, such as borax and kernite. The largest known boron deposits are in Turkey, the largest producer of boron minerals.

Elemental boron is a metalloid that is found in small amounts in meteoroids but chemically uncombined boron is not otherwise found naturally on Earth. Industrially, very pure boron is produced with difficulty because of refractory contamination by carbon or other elements. Several allotropes of boron exist: amorphous boron is a brown powder; crystalline boron is silvery to black, extremely hard (about 9.5 on the Mohs scale), and a poor electrical conductor at room temperature. The primary use of elemental boron is as boron filaments with applications similar to carbon fibers in some high-strength materials.

Boron is primarily used in chemical compounds. About half of all boron consumed globally is an additive in fiberglass for insulation and structural materials. The next leading use is in polymers and ceramics in high-strength, lightweight structural and refractory materials. Borosilicate glass is desired for its greater strength and thermal shock resistance than ordinary soda lime glass. Boron as sodium perborate is used as a bleach. A small amount of boron is used as a dopant in semiconductors, and reagent intermediates in the synthesis of organic fine chemicals. A few boron-containing organic pharmaceuticals are used or are in study. Natural boron is composed of two stable isotopes, one of which (boron-10) has a number of uses as a neutron-capturing agent.

In biology, borates have low toxicity in mammals (similar to table salt), but are more toxic to arthropods and are used as insecticides. Boric acid is mildly antimicrobial, and several natural boron-containing organic antibiotics are known.[12] Boron is an essential plant nutrient and boron compounds such as borax and boric acid are used as fertilizers in agriculture, although it's only required in small amounts, with excess being toxic. Boron compounds play a strengthening role in the cell walls of all plants. There is no consensus on whether boron is an essential nutrient for mammals, including humans, although there is some evidence it supports bone health.