Arsenic, ₃₃As

Arsenic
Pronunciation	/ˈɑːrsənɪk/ (AR-sən-ik) as an adjective: /ɑːrˈsɛnɪk/ (ar-SEN-ik)
Allotropes	grey (most common), yellow, black (see Allotropes of arsenic)
Appearance	metallic grey
Standard atomic weight Ar°(As)
	74.921595±0.000006[1] 74.922±0.001 (abridged)[2]
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 germanium ← arsenic → selenium
Atomic number (Z)	33
Group	group 15 (pnictogens)
Period	period 4
Block	p-block
Electron configuration	[Ar] 3d10 4s2 4p3
Electrons per shell	2, 8, 18, 5
Physical properties
Phase at STP	solid
Sublimation point	887 K ​(615 °C, ​1137 °F)
Density (at 20° C)	grey: 5.782 g/cm3[3]
when liquid (at m.p.)	5.22 g/cm3
Triple point	1090 K, ​3628 kPa[4]
Critical point	1673 K, ? MPa
Heat of fusion	grey: 24.44 kJ/mol
Heat of vaporization	34.76 kJ/mol (?)
Molar heat capacity	24.64 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,[5] +1,[6] +2, +3, +4, +5 (a mildly acidic oxide)
Electronegativity	Pauling scale: 2.18
Ionization energies	1st: 947.0 kJ/mol 2nd: 1798 kJ/mol 3rd: 2735 kJ/mol (more)
Atomic radius	empirical: 119 pm
Covalent radius	119±4 pm
Van der Waals radius	185 pm
Spectral lines of arsenic
Other properties
Natural occurrence	primordial
Crystal structure	grey: ​rhombohedral (hR2)
Lattice constants	ar = 413.15 pm α = 54.133° pm ah = 375.99 pm ch = 1054.58 pm (at 20 °C)[3]
Thermal expansion	5.6 µm/(m⋅K)[7] (at r.t.)
Thermal conductivity	50.2 W/(m⋅K)
Electrical resistivity	333 nΩ⋅m (at 20 °C)
Magnetic ordering	diamagnetic[8]
Molar magnetic susceptibility	−5.5×10−6 cm3/mol[9]
Young's modulus	8 GPa
Bulk modulus	22 GPa
Mohs hardness	3.5
Brinell hardness	1440 MPa
CAS Number	7440-38-2
History
Discovery	Arabic alchemists (before AD 815)
Isotopes of arsenic v e
Main isotopes[10] Decay abun­dance half-life (t1/2) mode pro­duct 73As synth 80.3 d ε 73Ge γ – 74As synth 17.8 d ε 74Ge β+ 74Ge γ – β− 74Se 75As 100% stable
Category: Arsenic view talk edit | references

Arsenic is a chemical element; it has 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 notoriously toxic metalloid. It has various allotropes, but only the grey 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. It is also a component of the III–V compound semiconductor gallium arsenide. Arsenic and its compounds, especially the trioxide, are used in the production of pesticides, treated wood products, herbicides, and insecticides. These applications are declining with the increasing recognition of the toxicity of arsenic and its compounds.^[11]

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.^[12][13] 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.^[14] 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.^[15] Arsenic is classified as a Group-A carcinogen.^[14]

Characteristics

Physical characteristics

Zdroj:https://en.wikipedia.org?pojem=Arsenic
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