Arsenic is a brittle element found in minerals such as arsenopyrite and used in specialized electronic materials. Gallium arsenide is a semiconductor, illustrating how pairing two elements produces a distinct material. Arsenic's chemical forms require careful identification because many arsenic-containing substances are poisonous.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
What makes arsenic a constituent of GaAs?
Gallium arsenide compound
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Form the compound semiconductor
Gallium and arsenic combine in gallium arsenide, creating a crystal whose electronic behavior belongs to the compound rather than either elemental material.
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AsFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
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What is arsenic's GaAs role?
Atomic identity, reference properties and structure models
INTERACTIVE 3D33 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Ar] 3d10 4s2 4p3. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Familiar minerals preceded an uncertain discovery record
Arsenic-bearing were known in ancient societies, but identifying the free element is a different historical question. Isolation is traditionally associated with Albertus Magnus in the thirteenth century. The evidence supports a cautious attribution rather than a precise modern discovery claim. The history also requires distinguishing the element from several compounds that shared older practical names.
Antiquity
Minerals used
Arsenic sulfide minerals were known before elemental isolation.
13th century
Traditional isolation attribution
Albertus Magnus is credited with isolation, with historical uncertainty.
Arsenopyrite is an important arsenic-bearing mineral that also contains iron and sulfur. Arsenic in such a mineral is part of a chemically combined structure, not a stored sample of the free element. Separating it therefore involves chemical changes as well as separating one material from another.
Arsenic's metallic-looking form is silver-gray and . Many arsenic compounds are hazardous, but their chemical properties still depend on composition and bonding. A mineral, a ingredient, and a dissolved compound therefore require separate descriptions rather than assuming that everything containing arsenic behaves like the free element.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
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Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
1090 K
at standard pressure unless noted Arsenic sublimes at standard pressure; melting requires elevated pressure.
Boiling point in K
887 K
101.325 kPa
Density in g/cm³
5.73 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
2.18 Pauling
Pauling scale
First ionization energy in kJ/mol
947 kJ/mol
gas-phase neutral atom, ground state
Covalent radius in pm
119 pm
single-bond covalent radius
Common oxidation states
-3, +3, +5
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust in mg/kg
1.8 mg/kg
upper continental crust, mass fraction
Has stable isotopes
Yesderived
Discovery year in CE
1250 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 4
As 2.18 Pauling · Arsenic
Electronegativity across period 4. Exact values.
K
0.82
Ca
1
Sc
1.36
Ti
1.54
V
1.63
Cr
1.66
Mn
1.55
Fe
1.83
Co
1.88
Ni
1.91
Cu
1.9
Zn
1.65
Ga
1.81
Ge
2.01
As
2.18
Se
2.55
Br
2.96
Kr
3
Electronegativity down group 15
As 2.18 Pauling · Arsenic
Electronegativity down group 15. Exact values.
N
3.04
P
2.19
As
2.18
Sb
2.05
Bi
2.02
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
