Stable isotope Argon (Ar)

Isotope Z(p) N(n) Atomic Mass Natural Abundance Enrichment Level Physical Form
Ar-36 18 18 35.9675462 0.34% ≥99.90% Gas
Ar-38 18 20 37.9627322 0.06% 99.90% Gas
Ar-40 18 22 39.96238312 99.60% 99.99% Gas

Properties of Argon

Name Argon
Symbol Ar
Atomic number 18
Atomic weight 39.948
Standard state Gas at 298 ºK
CAS Registry ID 7440-37-1
Group in periodic table 18
Group name Noble gas
Period in periodic table 3
Block in periodic table p-block
Color Colorless
Classification Nonmetallic
Melting point -189.3 ºC
Boiling point -185.8 ºC
Thermal conductivity 0.01772  W/(m-K)
Heat of vaporization 6.5  kJ·mol-1
Heat of fusion 1.18  kJ·mol-1
Density 1.784 g/cm3
Electron configuration [Ne]3s23p6
Oxidation state 0