Arsenic
Definition and meaning of Arsenic in chemistry.
![Arsenic element card: symbol As, atomic number 33, atomic mass 74.922, electron configuration [Ar] 3d¹⁰ 4s² 4p³, oxidation states +5 +3 -3, Metalloid, group 15, period 4, solid at room temperature.](/assets/images/terms/arsenic-chemical-element.webp)
Arsenic is a famous toxic element with the chemical symbol As and atomic number 33. It is a metalloid, which means it shows properties of both metals and nonmetals. Its most stable form is a brittle, gray crystal that conducts electricity moderately well.
In more detail
Arsenic sits in group 15 of the periodic table, just below phosphorus. The element easily shares valence electrons to form strong covalent bonds with other elements. It usually exhibits oxidation states of -3, +3, or +5 in its chemical compounds.
You can find arsenic scattered in trace amounts throughout the Earth's crust. It usually combines with sulfur and heavier metals to form various mineral compounds. The most common form of arsenic is the gray, metallic variety.
A less stable yellow form also exists, but it breaks down quickly at room temperature. If you heat solid arsenic in the air, it reacts rapidly with oxygen. This chemical reaction produces a white powder called arsenic trioxide, or As2O3.
During this heating process, the substance releases a very strong smell of garlic. Historically, people used arsenic compounds as pigments in green wallpapers and paints. However, damp environments caused mold to convert these pigments into toxic arsenic gases.
A common student misconception is that arsenic has no useful positive applications. In reality, manufacturers use tiny amounts of arsenic to make modern computer chips. They add it to silicon crystals through a process called semiconductor doping. This process adds extra negative charges to improve the flow of electrical currents.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | As |
| Atomic number | 33 |
| Atomic mass | 74.922 u |
| Category | Metalloid |
| Sublimation point | 615 °C (1139 °F) |
| Year discovered | Known since antiquity (c. 1250) |
Computer manufacturers add microscopic amounts of arsenic to silicon crystals for electronic devices. This addition increases the conductivity of the silicon by providing free valence electrons. The resulting semiconductor material is essential for building modern microchips and processors.
Frequently asked questions
Why is arsenic highly toxic to living organisms?
Arsenic stops cells from producing energy by blocking the essential enzymes needed for respiration.
Does arsenic melt when heated under normal conditions?
Under normal air pressure, solid arsenic turns directly into a gas without melting first.
How does arsenic help silicon chips carry electricity?
Arsenic has five valence electrons, while silicon only has four. Adding arsenic creates free electrons that carry electrical charge.
Related terms
Sources & references
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