Separated from natural gas by cryogenic distillation and adsorption: it stays gaseous below 20 K when everything else has already condensed, and pressure-swing adsorption on charcoal at 77 K finishes the cleanup.
Research Elements He · atomic number 2 Noble gas · period 1, group 18 1s2 Shells: 2 Valence electrons: 2 in the outer shell (1s2) 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).Helium
Electrons
How it's obtained
Natural isotopes
Isotope Relative atomic mass Abundance How this isotope is separated 3He 3.0160293201(25) 0.00000134(3) Product of tritium β decay in the weapons stockpile: 3H → 3He + e⁻ + ν̄ with a 12.3-year half-life. What’s needed for detectors and cryogenics is siphoned from the stockpile as tritium ages; a smaller amount is skimmed from natural gas by charcoal adsorption at 4 K. 4He 4.00260325413(6) 0.99999866(3)