The heaviest gas cut of cryogenic air distillation (Kr boils at 121 K), taken from the oxygen stream and cleaned up by charcoal adsorption.
Research Elements Kr · atomic number 36 Noble gas · period 4, group 18 [Ar] 3d10 4s2 4p6 Shells: 2, 8, 18, 8 Valence electrons: 8 in the outer shell (4s2 4p6) 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).Krypton
Electrons
How it's obtained
Natural isotopes
Isotope Relative atomic mass Abundance 78Kr 77.92036494(76) 0.00355(3) 80Kr 79.91637808(75) 0.02286(10) 82Kr 81.91348273(94) 0.11593(31) 83Kr 82.91412716(32) 0.11500(19) 84Kr 83.9114977282(44) 0.56987(15) 86Kr 85.9106106269(41) 0.17279(41)