Arsenic, As

Arsenic is a chemical element that has the symbol As and atomic number 33. Arsenic was first written about by Albertus Magnus (Germany) in 1250. Its Atomic Mass is 74.92. Its Ionic Charge is (3-) Its position in the periodic table is shown at right. This is a notoriously poisonous metalloid that has many allotropic forms: yellow (molecular non-metallic) and several black and gray forms (metalloids) are a few that are seen. Three metalloidal forms of arsenic with different crystal structures are found free in nature (the minerals arsenic sensu stricto and the much rarer arsenolamprite and pararsenolamprite), but it is more commonly found as arsenide and arsenate compounds. Several hundred such mineral species are known. Arsenic and its compounds are used as pesticides, herbicides, insecticides and various alloys.

The most common oxidation states for arsenic are -3 (arsenides: usually alloy-like intermetallic compounds), +3 (arsenates(III) or arsenites, and most organoarsenic compounds), and +5 (arsenates(V): the most stable inorganic arsenic oxycompounds). Arsenic also bonds readily to itself, forming, for instance, As-As pairs in the red sulfide realgar and square As43- ions in the arsenide skutterudite. In the +3 oxidation state, the stereochemistry of arsenic is affected by possession of a lone pair of electrons.

Technical Data
Symbol As Density (25°C)/gcm-3 5.778
Atomic number 33 Melting point / °C 8I6(8.6atm)
Atomic weight 74.9216 Boiling point / °C 613 (subl.)
Electronic configuration [Ar] 3d104s24p3 rcov(MIII single bond)/pm 120
Ionization energy/MJmol-1 III 0.947 rionic(6-coordinate)( MIII)/pm 58
II 1.798 (6-coordinate)(MV)/pm 46
III 2.736 Hardness (Mohs) 3.5
Sum (l+II+HI)/MJmol-1 5.481 Electrical resistivity (20°C)/μohm cm 33.3
Sum (IV+V)/MJmol-4 10.88 Contraction on freezing/% 10
Electronegativity χ 2    
Evaporation Techniques
Temperature (oC) @Vap. Pressure Techniques Remarks
10-8 Torr 10-6 Torr 10-4 Torr Electron Beam Crucible Coil Boat
107 Sublimes 150 Sublimes 210 Sublimes Poor Vitreous graphite & Al2O3   Carbon Toxic, sublimes rapidly at low temperature.

Evaporation Materials
A3-5000-M Pieces 2-6mm
A3-5001-M Pieces 3-12mm
A3-5003-M Pieces 8-20mm
A3-10000-P -20 mesh
A3-10002-P -100 mesh
A3-10003-P -325 mesh (<10 microns)