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Arsenic is used as the group 15 element in the III-V semiconductors gallium arsenide, indium arsenide, and aluminium arsenide. [10] The valence electron count of GaAs is the same as a pair of Si atoms, but the band structure is completely different which results in distinct bulk properties. [11]
An atom with a closed shell of valence electrons (corresponding to a noble gas configuration) tends to be chemically inert. Atoms with one or two valence electrons more than a closed shell are highly reactive due to the relatively low energy to remove the extra valence electrons to form a positive ion. An atom with one or two electrons fewer ...
The light pnictogens (nitrogen, phosphorus, and arsenic) tend to form −3 charges when reduced, completing their octet. When oxidized or ionized, pnictogens typically take an oxidation state of +3 (by losing all three p-shell electrons in the valence shell) or +5 (by losing all three p-shell and both s-shell electrons in the valence shell).
Arsenic has a similar electronegativity and ionization energies to its lighter pnictogen congener phosphorus and therefore readily forms covalent molecules with most of the nonmetals. Though stable in dry air, arsenic forms a golden-bronze tarnish upon exposure to humidity which eventually becomes a black surface layer. [31]
When arsenic(III) is present, a brown coloration appears forming a dark precipitate of arsenic, according to the following simplified reaction: 2 As 3+ + 3 Sn 2+ → 2 As 0 + 3 Sn 4+ Here three tin atoms are oxidized from oxidation state +2 to +4, yielding six electrons that reduce two arsenic atoms from oxidation state +3 to 0. The simple one ...
The noble gases have full valence electron shells. Valence electrons are the outermost electrons of an atom and are normally the only electrons that participate in chemical bonding. Atoms with full valence electron shells are extremely stable and therefore do not tend to form chemical bonds and have little tendency to gain or lose electrons. [35]
Arsenic, sealed in a container to prevent tarnishing. Arsenic is a grey, metallic looking solid which is stable in dry air but develops a golden bronze patina in moist air, which blackens on further exposure. It has a density of 5.727 g/cm 3, and is brittle and moderately hard (MH 3.5; more than aluminium; less than iron). Arsenic sublimes at ...
Arsenic and antimony are not semiconductors in their standard states. Both form type III-V semiconductors (such as GaAs, AlSb or GaInAsSb) in which the average number of valence electrons per atom is the same as that of Group 14 elements, but they have direct band gaps. These compounds are preferred for optical applications. [206]