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:

As 2006: Natural Arsenic in Groundwaters of Latin America | EVISA's Agenda of Events
Directory of scientists: Kevin A. Francesconi
Material database: FAPAS - Test Material T0797 (Canned Fish)
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-422
Material database: Fluka Chemie GmbH - Arsenobetaine
Trace element speciation for environmental analysis | EVISA's News
Arsenic species in human milk | EVISA's News
Atomic Fluorescence Spectrometry as a Detection System for Speciation Analysis | EVISA's News
Instrument database: Analytik Jena AG - contrAAź 800 G - Graphite Furnace Atomic Absorption Spectrometer
Material database: Sigma-Aldrich - Matrix CRM - Soil, Sludge, Sediment: Trace Metals - Sandy Loam 9
Material database: IAEA - MEL International Atomic Energy Agency - IAEA-433 Trace Elements and Methylmercury in Marine Sediment
Link database: US FDA: Product Safety Information: 3-Nitro (Roxarsone) and Chicken
New arsenic compounds found in herring | EVISA's News
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-397 - Trace elements in human hair
Material database: FAPAS - Test Material T07112 (Canned Crab Meat)
Accurate determination of arsenic and its species by internal standardization | EVISA's News
Toxicity of organoarsenicals revisited | EVISA's News
Material database: National Institute of Standards and Technology (NIST) - SRM 663 - Chromium-Vanadium Steel (Modified)
Material database: National Analysis Center for Iron & Steel (NACIS) - NCS ZC73013 - Trace Elements in Spinach
Material database: National Institute of Standards and Technology (NIST) - SRM 1635a - Trace Elements in Coal, (Subbitumimous)