Arsenic is a chemical element that has the symbol As and atomic number 33. Its Atomic Mass is 74.92. Its Ionic Charge is (3-). 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 strictu 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.

The term "arsenic" was found in the following pages:

Material database: National Metrology Institute of Japan (NMIJ) - NMIJ CRM 7901-a - Arsenobetaine solution
Material database: SUPELCO by Sigma-Aldrich - Arsenic(III) sulfide
Methylmercury in fish: Can you cook it out ? | EVISA's News
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Clay 1
Material database: American Elements - Triphenylarsine Oxide
Link database: Metal Speciation Toxicokinetics Database: Arsenic
Material database: National Institute of Standards and Technology (NIST) - SRM 955c - Toxic Elements in Caprine Blood /Level 3
Link database: IMOA: Molybdenum - Physiological effects and toxicity
Material database: Institute of Nuclear Chemistry and Technology (INCT/ICHTJ) - CTA-OTL-1 ORIENTAL TOBACCO LEAVES
Instrument database: JEOL - JSX-3202EV
Material database: RECIPE Chemicals + Instruments GmbH - ClinChek 8883 Control blood plasma, lyophilised, trace elements level I: LOT 1286
Material database: The Food and Environment Research Agency (FAPAS) - Test Material T07155 (Soft Drink)
Council Decision 75/437/EEC on Marine Pollution from Land-based Sources | EVISA's News
EFSA publishes dietary reference value for manganese | EVISA's News
Link database: National Emission Standards for Hazardous Air Pollutants; Standards for Inorganic Arsenic
Directory of scientists: Andreas Kappler
Material database: National Metrology Institute of Japan (NMIJ) - NMIJ CRM 7402-a: Trace Elements, Arsenobetaine and Methylmercury in Cod Fish Tissue
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-278R
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Sewage Amended Soil
Arsenic species distribution in drinking water wells in the USA with high arsenic concentrations | EVISA's News