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 Institute of Standards and Technology (NIST) - SRM 1649a - Urban Dust
Arsenic Speciation in Rice Cereals for Infants | EVISA's News
Researchers found new sulfur-containing metabolites in the urine of rats exposed to arsenite | EVISA's News
Material database: National Research Council of Canada (NRC - CNRC) - SPIN-1: Air-dried Spinach Powder Certified Reference Material for Nitrate and Trace Metals
Directory of scientists: Entwisle John
X ISTERH 2013: International Society of Trace Element Research in Humans | EVISA's Agenda of Events
Material database: National Institute of Standards and Technology (NIST) - SRM 3030 - Monomethylarsonic Acid Standard Solution
Material database: IRMM - Institute for Reference Materials and Measurements - BCR-288
High Levels of Arsenic in American Wines | EVISA's News
Link database: US FDA: Analysis of Foods for As, Cd, Cr, Hg and Pb by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)
Toxic mine cleanup may get help from arsenic-loving bacteria | EVISA's News
Material database: National Institute of Standards and Technology (NIST) - SRM 83d - Arsenic Trioxide (Reductometric)
Instrument database: Physical Electronics - ADEPT-1010 D-SIMS
Link database: Metal Speciation Toxicokinetics Database: Arsenic
Directory of scientists: Zdenka Šlejkovec
Accurate determination of arsenic and its species by internal standardization | EVISA's News
Link database: Hazardous Substances Data Bank: Arsenic Pentoxide
Material database: JRC - Joint Research Centre - ERM-CE278 - Mussel tissue (mytilus edulis)
Material database: JRC - Joint Research Centre - ERM-BB422 - Fish muscle
Atomic Fluorescence Spectrometry as a Detection System for Speciation Analysis | EVISA's News