|Molar mass||74.9216 g mol−1|
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
In chemistry, an arsenide is a compound of arsenic with a less electronegative element or elements. Most metals form arsenides. There are a large number of different stoichiometries and in this respect arsenides are similar to phosphides, borides, silicides and nitrides. The group 1 alkali metals and the group 2, alkaline earth metals, form arsenides with isolated arsenic atoms which can be considered to be the As3− anion, for example heating arsenic powder with excess sodium gives sodium arsenide (Na3As). The As3− ion is formed by the reduction of arsenic by three electrons. The structure of Na3As is complex with unusually short Na–Na distances of 328–330 pm which are shorter than in sodium metal, and this is indicates that even with these electropositive metals the bonding cannot be straightforward ionic. The compound LiAs, has a metallic lustre and electrical conductivity indicating some metallic bonding. A number of arsenide minerals are known, for example nickeline, NiAs, skutterudite, CoAs3 (a diamagnetic semiconductor) Assigning formal oxidation numbers (states) is difficult unless the structure is known, for example the mineral sperrylite (PtAs2), platinum arsenide, has a formal oxidation state for arsenic of –2. as the solid is usually described as Pt4+,As24−. The description of gallium arsenide (GaAs) is more straightforward since it features isolated arsenic centers, however as it is a III–V semiconductor with a wurtzite structure the bonding is predominantly covalent.
Arsenides are toxic because of the inherent toxicity of arsenic and all of its compounds.
Metal arsenides react with acids to form highly toxic arsine gas.
See category for a list.
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