About

Arsenic is a metalloid that is notoriously toxic in its inorganic forms. In its common metallic gray form, it is brittle and crystalline. Despite its reputation as a poison, it has important uses, such as strengthening lead alloys for batteries and as a key n-type dopant in semiconductors. Gallium arsenide (GaAs) is a crucial compound for high-speed integrated circuits and LEDs.

Atomic Properties

Atomic Number33

Atomic Weight74.922 u

Neutrons (common)42

Electron Configuration[Ar] 3d¹⁰ 4s² 4p³

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³

Electrons per Shell2, 8, 18, 5

Electronegativity2.18

Electron Affinity77.65 kJ/mol

Oxidation States+5, +3, -3

Covalent Radius119 pm

Van der Waals Radius185 pm

Ionic Radius58 pm

Periodic Table Position

Group15

Period4

BlockP

Chemical SeriesMetalloids

Physical Properties

State at STPsolid

Appearancesteel-grey, brittle metalloid

Crystal Structurerhombohedral

Magnetic Orderingdiamagnetic

Thermal Properties

Melting Point1,090 K

Sublimation Point887 K

Triple Point1,090 K

Thermal Expansion0 1/K

Thermal Conductivity50.2 W/(m·K)

Specific Heat0.329 J/(g·K)

Molar Heat24.64 J/(mol·K)

Heat of Fusion27.7 kJ/mol

Heat of Vaporization34.76 kJ/mol

Abundance

In Earth's Crust1.8 ppm

In Ocean0.004 ppm

In Solar System0.008 ppm

In Human Body0.1 ppm

In Universe0.008 ppm

Discovery

Discovered byAlbertus Magnus

Discovery Yearc. 1250

Occurrenceprimordial

CAS Number7440-38-2

Electron Configuration

Energy

↿⇂

↿

Isotopes of Arsenic

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
⁷³As	72.923825	—	80.30 d	Electron Capture
⁷⁴As	73.923928	—	17.77 d	Positron Emission, Electron Capture, Beta Minus Decay
⁷⁵As	74.921600	100%	Stable	Stable

Interactive Visualization

Explore the 3D Bohr model of Arsenic in our interactive viewer.

View 3D Model of Arsenic