Ar

Argon

Identification

CAS Number: 7440-37-1

Discovery Year: 1894

Discoverer: Sir William Ramsey, Baron Rayleigh

Discovery Location: Scotland

Properties

Atomic Mass: 39.948 →Density: 0.001633 g/cm³ →

Crust Abundance: 3.5 mg/kg

Crystal Structure: FCC

Atomic Dimensions

Atomic Radius: 71 pm →

Atomic Radius (Rahm): 197 pm

Covalent Radius: 106 pm →

Van der Waals Radius: 188 pm

Atomic Volume: 24.2 cm³/mol

Lattice Constant: 5.26 Å

Thermodynamics

Melting Point: 83.8 K →Boiling Point: 87.3 K →Specific Heat: 0.138 J/(g·K) →Thermal Conductivity: 0.0177 W/(m·K) →Heat of Vaporization: 6.52 kJ/mol →

Electronic Structure

Electron Config: [Ne] 3s2 3p6

Block: p

Period: 3 →Group: 18 →Electron Affinity: -11.5 eV →

Oxidation States: 0

Abundance & Geochemistry

Crust Abundance: 3.5 mg/kg

Sea Abundance: 0.45 mg/L

Geochemical Class: volatile

Goldschmidt Class: atmophile

About

Argon is a colorless, odorless noble gas that makes up about 1% of Earth's atmosphere. It is used in welding, light bulbs, and as an inert atmosphere.

Isotopes

Ar-40 40 99.60%

Ar-36 36 0.3336%

Ar-38 38 0.0629%