Arsenic is often called the "king of poisons". All forms of arsenic, whether pure or in a compound, are poisonous to animals. In fact, arsenic poisons have been used for centuries.

This semi-metal is found in several brightly colored minerals, including oropiment. Naturally occurring pure arsenic has a bright gray color. Arsenic compounds are used to make some rat poisons. The main use of arsenic today is to fortify lead. This is done by mixing arsenic with lead to create a strong alloy that is often used in automobile batteries.

Summary of properties (As)

Atomic weight74.921595(6)
Discoverer (year)Magnus, Albertus (1886)
Natural formnon-metal solid (rhombohedral)
Electron configuration[Ar] 3d10 4s2 4p3
Melting point (ºC)816.8
Boiling point (ºC)613
Abundance in earth's crust (ppm)1.8
Isotope (abundance)75As (100)
Density g/cm35.72
Van der Waals radius (pm)185
Covalent radius (pm)120
Electronegativity (Pauling)2.55
Vaporization enthalpy (kJ/mol)31.90
Enthalpy of fusion (kJ/mol)24.44
Specific heat capacity (J/g·K) at 25ºC and 1 atm0.33
Thermal conductivity (W/cm·K) at 25ºC and 1 atm0.500
Oxidation state+5, +3, -3
Electron affinity (eV)0.80
1st Ionization potential (eV)9.7886

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