Arsenic valence state and bonding

In crystalline substances, arsenic forms covalent bonds with itself and most other elements. That is, an arsenic atom in a covalent bond shares its valence electrons with another atom in the bond. However, unless arsenic atoms bond to each other, the valence electrons in a covalent bond are not equally shared between the arsenic atom and the atom of the other element. That is, most of the covalent bonds still have an ionic character to them (Faure, 1998), 83-89. 

Like sulfide in pyrite, arsenic in arsenic-rich (arsenian) pyrite (FeS2) and many arsenide and arseno-sulflde minerals has a valence state of — 1 or 0. These valence states result from arsenic forming covalent bonds with other arsenic atoms or sulfur (Klein, 2002), 340, 369 (Foster, 2003), 35 (O Day, 2006), 80. In the arsenide niccolite (also called nickeline, NiAs), every nickel atom is surrounded by six arsenic atoms, where arsenic has a valence state of —1 and nickel is +1 (Klein, 2002), 360 (Foster, 2003), 35. The 

Arsenic isotope Number of neutrons Atomic mass Half-life Decay mode 

Valence state Coordination number Radius (A) and reference(s) 

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