A middle cut from cryogenic air distillation: Ar boils at 87 K, close to O2 at 90 K, so a second column trims off the last of the O2 catalytically over Pd.
Research Elements Ar · atomic number 18 Noble gas · period 3, group 18 [Ne] 3s2 3p6 Shells: 2, 8, 8 Valence electrons: 8 in the outer shell (3s2 3p6) Green dots are the outer shell's s and p electrons. Softer green dots are the d electrons of transition metals, and the d and f electrons of lanthanides and actinides: they often take part in bonding, but not always. Grey dots are the core. Ground-state configuration from the NIST Atomic Spectra Database (A. Kramida, Yu. Ralchenko, J. Reader and the NIST ASD Team). Abundance is the mole fraction of the element found as that isotope on Earth; digits in parentheses are the uncertainty in the last digits. Masses and abundances from NIST, Atomic Weights and Isotopic Compositions (J. S. Coursey, D. J. Schwab, J. J. Tsai and R. A. Dragoset, National Institute of Standards and Technology).Argon
Electrons
How it's obtained
Natural isotopes
Isotope Relative atomic mass Abundance 36Ar 35.967545105(28) 0.003336(21) 38Ar 37.96273211(21) 0.000629(7) 40Ar 39.9623831237(24) 0.996035(25)