In chemistry, an arsenide is a compound of

arsenic 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, ...

with a less

electronegative Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...

element or elements. Many metals form

binary compound In materials chemistry, a binary phase or binary compound is a chemical compound containing two different elements. Some binary phase compounds are molecular, e.g. carbon tetrachloride (CCl4). More typically binary phase refers to extended soli ...

s containing arsenic, and these are called arsenides. They exist with many stoichiometries, and in this respect arsenides are similar to

phosphide In chemistry, a phosphide is a compound containing the ion or its equivalent. Many different phosphides are known, with widely differing structures. Most commonly encountered on the binary phosphides, i.e. those materials consisting only of phos ...

Alkali metal and alkaline earth arsenides

The group 1 alkali metals and the group 2,

alkaline earth metal The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are all ...

s, form arsenides with isolated arsenic atoms. They form upon heating arsenic powder with excess sodium gives sodium arsenide (Na₃As). The structure of Na₃As is complex with unusually short Na–Na distances of 328–330 pm which are shorter than in sodium metal. This short distance indicates the complex bonding in these simple phases, i.e. they are not simply salts of As³⁻ anion, for example. The compound LiAs, has a metallic lustre and electrical conductivity indicating some metallic bonding. These compounds are mainly of academic interest. For example, "sodium arsenide" is a structural motif adopted by many compounds with the A₃B stoichiometry. Indicative of their salt-like properties, hydrolysis of alkali metal arsenides gives

arsine Arsine (IUPAC name: arsane) is an inorganic compound with the formula As H3. This flammable, pyrophoric, and highly toxic pnictogen hydride gas is one of the simplest compounds of arsenic. Despite its lethality, it finds some applications in ...

: :Na₃As + 3 H₂O → AsH₃ + 3 NaOH

III–V compounds

Many arsenides of the group 13 elements (group III) are valuable semiconductors. Gallium arsenide (GaAs) features isolated arsenic centers with a

zincblende Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in sedimentary exhalative, Mississippi-Va ...

structure (

wurtzite Wurtzite is a zinc and iron sulfide mineral with the chemical formula , a less frequently encountered structural polymorph form of sphalerite. The iron content is variable up to eight percent.Palache, Charles, Harry Berman & Clifford Frondel (19 ...

structure can eventually also form in nanostructures), and with predominantly covalent bonding – it is a III–V semiconductor.

II–V compounds

Arsenides of the group 12 elements (group II) are also noteworthy. Cadmium arsenide (Cd₃As₂) was shown to be a three-dimensional (3D) topological Dirac

semimetal A semimetal is a material with a very small overlap between the bottom of the conduction band and the top of the valence band. According to electronic band theory, solids can be classified as insulators, semiconductors, semimetals, or metals ...

analogous to

graphene Graphene () is an allotrope of carbon consisting of a single layer of atoms arranged in a hexagonal lattice nanostructure.

. Cd₃As₂, Zinc arsenide, Zn₃As₂ and other compounds of the Zn-Cd-P-As quaternary system have very similar crystalline structures, which can be considered distorted mixtures of the zincblende and

antifluorite In solid state chemistry, the fluorite structure refers to a common motif for compounds with the formula MX2. The X ions occupy the eight tetrahedral interstitial sites whereas M ions occupy the regular sites of a face-centered cubic (FCC) structure ...

crystalline structures.

Polyarsenides

Transition metal arsenides

Arsenic anionics are known to catenate, that is, form chains, rings, and cages. The mineral

skutterudite Named after Skuterudåsen, a hill in Modum, Norway, skutterudite is a cobalt arsenide mineral containing variable amounts of nickel and iron substituting for cobalt with the ideal formula CoAs3. Some references give the arsenic a variable formula ...

(CoAs₃) features rings that are usually described as . Assigning formal oxidation numbers is difficult because these materials are highly covalent and often are best described with band theory.

Sperrylite Sperrylite is a platinum arsenide mineral with the chemical formula and is an opaque metallic tin white mineral which crystallizes in the isometric system with the pyrite group structure. It forms cubic, octahedral or pyritohedral crystals in ...

(PtAs₂) is usually described as . The arsenides of the transition metals are mainly of interest because they contaminate sulfidic ores of commercial interest. The extraction of the metals – nickel, iron, cobalt, copper – entails chemical processes such as smelting that poses environmental risks. In the mineral, arsenic is immobile and poses no environmental risk. Released from the mineral, arsenic is poisonous and mobile.

Zintl phases

Partial reduction of arsenic with alkali metals (and related electropositive elements) affords polyarsenic compounds, which are members of the

Zintl phase In chemistry, a Zintl phase is a product of a reaction between a group 1 (alkali metal) or group 2 ( alkaline earth metal) and main group metal or metalloid (from groups 13, 14, 15, or 16). It is characterized by intermediate metallic/ ionic bond ...

References

Anions Arsenic(−III) compounds {{Inorganic-compound-stub