Arsenic

Atomic number

33

Atomic mass (u)

74.92159

Category

Metalloid

Standard state

Solid

Melting point

816.85 °C (1090 K)

Boiling point

613.85 °C (887 K)

Density (g/cm³)

5.776

Electronegativity (Pauling)

2.18

Electron configuration

[Ar]4s2 3d10 4p3

Oxidation states

+5, +3, -3

Atomic radius (pm)

185

First ionization energy (eV)

9.815

Discovery & recognition

Discovery year / period (PubChem)

Ancient

Discovery credited to (RSC)

Albertus Magnus

Date or period recorded by RSC

approx 1250

Discovery place

Known since antiquity; no single first-discovery place is established.

An ancient date does not identify a first human discovery. Different references may date observation, isolation and formal recognition differently.

Natural occurrence & production

The creation of an element’s nuclei and its concentration into terrestrial deposits are different processes. The occurrence note below concerns its presence or production on Earth; it is not a complete account of nucleosynthesis.

“A small amount of arsenic is found in its native state.”

Royal Society of Chemistry · occurrence excerpt ↗

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Reference values are not product specifications. Blank values have not been estimated. For superheavy elements, some properties and family assignments are theoretical or incompletely measured.