33
As
Arsenic
74.9216
Arsenic (As)
MetalloidGroup 15Period 4p-block-block
Arsenic is a chemical element with symbol As and atomic number 33. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. Arsenic is a metalloid.
Latin name: Arsenicum
Atomic Number
33
Atomic Mass
74.9216 g/mol
Phase (STP)
Solid
Electron Config.
[Ar] 3d¹⁰ 4s² 4p³
General
SymbolAs
Atomic Number33
Atomic Mass74.9216 g/mol
CategoryMetalloid
Group15
Period4
Blockp-block
Electron Configuration[Ar] 3d¹⁰ 4s² 4p³
Valence Electrons5
Colourmetallic gray
Appearancemetallic grey
CAS NumberCAS7440-38-2
Physical Properties
Phase (STP)Solid
Density5.727 g/cm³
Melting Point816.85°C · 1502.33°F · 1090.00 K
Boiling Point613.85°C · 1136.93°F · 887.00 K
Atomic Properties
Atomic Radius114 pm
Electronegativity2.18 Pauling
Ionization Energy947 kJ/mol
Oxidation States+5, +3, -3
Ion ChargeAs3-/As3+/As5+
Thermodynamic
Molar Heat24.64 J/(mol·K)
Crystal Structure
Crystal Structurerhombohedral
Mechanical Properties
Mohs Hardness3.5
Abundance
In Earth's Crust0.0180%
Discovery & History
Discovered ByAlbertus Magnus (isolated)
Country of DiscoveryGermany
Isotopes of Arsenic
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| As-73 | — | 80.30 days | EC |
| As-75 | 100% | Stable | — |