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Arsenic (As)

Arsenic is a chemical element of the periodic table with chemical symbol As and atomic number 33 with an atomic weight of 74.9216 u and is classed as metalloid and is part of group 15 (nitrogen group). Arsenic is solid at room temperature.

Arsenic in the periodic table

Atomic number33
Group15 (Nitrogen group)
AppearanceMetallic grey
Color Silver
Number of protons33 p+
Number of neutrons42 n0
Number of electrons33 e-
From Wikipedia, the free encyclopediaArsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid.

Physical properties

Phase at STPSolid
Density5.727 g/cm3
Atomic weight74.9216 u

Thermal properties

Melting point-
Boiling point-
Heat of vaporization32.4 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)2.18
Electron affinity77.65 kJ/mol
Oxidation states−3, −2, −1, 0, +1, +2, +3, +4, +5
(a mildly acidic oxide)
Ionization energies
  1. 947 kJ/mol
  2. 1798 kJ/mol
  3. 2735 kJ/mol
  4. 4837 kJ/mol
  5. 6043 kJ/mol
  6. 12310 kJ/mol

Electron configuration for arsenic

Electron configuration
Shorthand configuration
[Ar] 3d10 4s2 4p3
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3
Electron configuration chart
Electrons per shell2, 8, 18, 5
Valence electrons 5
Valency electrons 5,3
Bohr model
ArsenicElectron shell for Arsenic, created by Injosoft ABAs
Figure: Shell diagram of Arsenic (As) atom.
Orbital Diagram

The history of Arsenic

DiscoveryMiddle-Eastern alchemists (815)
Discovery of arsenic
During the Bronze Age, arsenic was often included in bronze, which made the alloy harder (so-called "arsenical bronze"). The isolation of arsenic was described by Muslim alchemist Jabir ibn Hayyan before 815 AD. Albertus Magnus (Albert the Great, 1193–1280) later isolated the element from a compound in 1250, by heating soap together with arsenic trisulfide. In 1649, Johann Schröder published two ways of preparing arsenic. Crystals of elemental (native) arsenic are found in nature, although rare.


List of unique identifiers for Arsenic in various chemical registry databases
CAS Number7440-38-2
ChemSpider ID4514330
EC number231-148-6
PubChem CID Number5359596