Arsenic
Definition and meaning of Arsenic in chemistry.
Arsenic is a notoriously toxic metalloid represented by the chemical symbol As and atomic number 33. It exists in multiple allotropic forms, the most stable being a steel-gray, brittle crystalline solid that is utilized extensively in modern semiconductor doping processes.
In more detail
Located in group 15 of the periodic table, arsenic readily forms strong covalent bonds and exhibits primary oxidation states of -3, +3, and +5 in its various complex molecular compounds. It is most commonly found scattered throughout the Earth's crust combined with sulfur and heavier metals, notably in common minerals like arsenopyrite, or occasionally extracted as a pure native crystal in hydrothermal veins. The standard gray allotrope conducts electricity moderately well as a semimetal, while the contrasting yellow allotrope is a poor electrical conductor and remains highly unstable at normal room temperatures. Upon heating in an oxygen-rich atmosphere, arsenic rapidly oxidizes to form arsenic trioxide (As2O3), simultaneously producing a distinctive, pungent odor that closely resembles the scent of fresh garlic. Despite its historical reputation as a potent biological poison, trace amounts are purposefully introduced into modern silicon semiconductors to precisely alter their electrical conductive properties through a deliberate manufacturing process known as doping.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | As |
| Atomic number | 33 |
| Atomic mass | 74.922 u |
| Category | Metalloid |
| State at room temperature | Solid |
| Sublimation point | 615 °C (1139 °F) |
| Year discovered | Known since antiquity (c. 1250) |
Small microscopic fractions of arsenic are used to dope silicon and germanium semiconductors, providing excess mobile electrons that create n-type semiconducting materials for manufacturing modern transistors.
Frequently asked questions
Why is arsenic highly toxic to living organisms?
Arsenic disrupts vital cellular respiration processes by inhibiting critical metabolic enzymes involved in ATP energy production, effectively starving biological cells of their necessary energy supply.
Does arsenic melt when heated under normal conditions?
At standard atmospheric pressure, solid arsenic sublimes directly into a gas rather than melting, requiring exceptionally high environmental pressure to force it to form a liquid phase.