Arsenic

  • arsenic, 33as
    arsen 1a.jpg
    arsenic
    pronunciation
    • k/
      (ars-nik)
    • as an adjective: k/
      (sen-ik)
    allotropesgrey (most common), yellow, black
    appearancemetallic grey
    standard atomic weight ar, std(as)74.921595(6)[1]
    arsenic 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
    p

    as

    sb
    germaniumarsenicselenium
    atomic number (z)33
    groupgroup 15 (pnictogens)
    periodperiod 4
    blockp-block
    element category  metalloid
    electron configuration[ar] 3d10 4s2 4p3
    electrons per shell2, 8, 18, 5
    physical properties
    phase at stpsolid
    sublimation point887 k ​(615 °c, ​1137 °f)
    density (near r.t.)5.727 g/cm3
    when liquid (at m.p.)5.22 g/cm3
    triple point1090 k, ​3628 kpa[2]
    critical point1673 k, ? mpa
    heat of fusiongrey: 24.44 kj/mol
    heat of vaporization34.76 kj/mol (?)
    molar heat capacity24.64 j/(mol·k)
    vapor pressure
    p (pa) 1 10 100 1 k 10 k 100 k
    at t (k) 553 596 646 706 781 874
    atomic properties
    oxidation states−3, −2, −1, 0,[3] +1,[4] +2, +3, +4, +5 (a mildly acidic oxide)
    electronegativitypauling scale: 2.18
    ionization energies
    • 1st: 947.0 kj/mol
    • 2nd: 1798 kj/mol
    • 3rd: 2735 kj/mol
    • (more)
    atomic radiusempirical: 119 pm
    covalent radius119±4 pm
    van der waals radius185 pm
    color lines in a spectral range
    spectral lines of arsenic
    other properties
    natural occurrenceprimordial
    crystal structurerhombohedral
    rhombohedral crystal structure for arsenic
    thermal expansion5.6 µm/(m·k)[5] (at r.t.)
    thermal conductivity50.2 w/(m·k)
    electrical resistivity333 nΩ·m (at 20 °c)
    magnetic orderingdiamagnetic[6]
    magnetic susceptibility−5.5·10−6 cm3/mol[7]
    young's modulus8 gpa
    bulk modulus22 gpa
    mohs hardness3.5
    brinell hardness1440 mpa
    cas number7440-38-2
    history
    discoveryarabic alchemists (before ad 815)
    main isotopes of arsenic
    iso­tope abun­dance half-life (t1/2) decay mode pro­duct
    73as syn 80.3 d ε 73ge
    γ
    74as syn 17.8 d ε 74ge
    β+ 74ge
    γ
    β 74se
    75as 100% stable
    category category: arsenic
    | references

    arsenic is a chemical element with the symbol as and atomic number 33. arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. arsenic is a metalloid. it has various allotropes, but only the gray form, which has a metallic appearance, is important to industry.

    the primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition). arsenic is a common n-type dopant in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the second most commonly used semiconductor after doped silicon. arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. these applications are declining due to the toxicity of arsenic and its compounds.[8]

    a few species of bacteria are able to use arsenic compounds as respiratory metabolites. trace quantities of arsenic are an essential dietary element in rats, hamsters, goats, chickens, and presumably other species. a role in human metabolism is not known.[9][10][11] however, arsenic poisoning occurs in multicellular life if quantities are larger than needed. arsenic contamination of groundwater is a problem that affects millions of people across the world.

    the united states' environmental protection agency states that all forms of arsenic are a serious risk to human health.[12] the united states' agency for toxic substances and disease registry ranked arsenic as number 1 in its 2001 priority list of hazardous substances at superfund sites.[13] arsenic is classified as a group-a carcinogen.[12]

  • characteristics
  • compounds
  • occurrence and production
  • history
  • applications
  • biological role
  • essential trace element in higher animals
  • environmental issues
  • toxicity and precautions
  • see also
  • references
  • bibliography
  • further reading
  • external links

Arsenic, 33As
Arsen 1a.jpg
Arsenic
Pronunciation
Allotropesgrey (most common), yellow, black
Appearancemetallic grey
Standard atomic weight Ar, std(As)74.921595(6)[1]
Arsenic 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
P

As

Sb
germaniumarsenicselenium
Atomic number (Z)33
Groupgroup 15 (pnictogens)
Periodperiod 4
Blockp-block
Element category  Metalloid
Electron configuration[Ar] 3d10 4s2 4p3
Electrons per shell2, 8, 18, 5
Physical properties
Phase at STPsolid
Sublimation point887 K ​(615 °C, ​1137 °F)
Density (near r.t.)5.727 g/cm3
when liquid (at m.p.)5.22 g/cm3
Triple point1090 K, ​3628 kPa[2]
Critical point1673 K, ? MPa
Heat of fusiongrey: 24.44 kJ/mol
Heat of vaporization34.76 kJ/mol (?)
Molar heat capacity24.64 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 553 596 646 706 781 874
Atomic properties
Oxidation states−3, −2, −1, 0,[3] +1,[4] +2, +3, +4, +5 (a mildly acidic oxide)
ElectronegativityPauling scale: 2.18
Ionization energies
  • 1st: 947.0 kJ/mol
  • 2nd: 1798 kJ/mol
  • 3rd: 2735 kJ/mol
  • (more)
Atomic radiusempirical: 119 pm
Covalent radius119±4 pm
Van der Waals radius185 pm
Color lines in a spectral range
Spectral lines of arsenic
Other properties
Natural occurrenceprimordial
Crystal structurerhombohedral
Rhombohedral crystal structure for arsenic
Thermal expansion5.6 µm/(m·K)[5] (at r.t.)
Thermal conductivity50.2 W/(m·K)
Electrical resistivity333 nΩ·m (at 20 °C)
Magnetic orderingdiamagnetic[6]
Magnetic susceptibility−5.5·10−6 cm3/mol[7]
Young's modulus8 GPa
Bulk modulus22 GPa
Mohs hardness3.5
Brinell hardness1440 MPa
CAS Number7440-38-2
History
DiscoveryArabic alchemists (before AD 815)
Main isotopes of arsenic
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
73As syn 80.3 d ε 73Ge
γ
74As syn 17.8 d ε 74Ge
β+ 74Ge
γ
β 74Se
75As 100% stable
Category Category: Arsenic
| references

Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but only the gray form, which has a metallic appearance, is important to industry.

The primary use of arsenic is in alloys of lead (for example, in car batteries and ammunition). Arsenic is a common n-type dopant in semiconductor electronic devices, and the optoelectronic compound gallium arsenide is the second most commonly used semiconductor after doped silicon. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining due to the toxicity of arsenic and its compounds.[8]

A few species of bacteria are able to use arsenic compounds as respiratory metabolites. Trace quantities of arsenic are an essential dietary element in rats, hamsters, goats, chickens, and presumably other species. A role in human metabolism is not known.[9][10][11] However, arsenic poisoning occurs in multicellular life if quantities are larger than needed. Arsenic contamination of groundwater is a problem that affects millions of people across the world.

The United States' Environmental Protection Agency states that all forms of arsenic are a serious risk to human health.[12] The United States' Agency for Toxic Substances and Disease Registry ranked arsenic as number 1 in its 2001 Priority List of Hazardous Substances at Superfund sites.[13] Arsenic is classified as a Group-A carcinogen.[12]