Property Helium Neon Argon Krypton Xenon Radon Density (g / dm) 0.1786 0.9002 1.7818 3.708 5.851 9.97 Boiling point (K) 4.4 27.3 87.4 121.5 166.6 211.5 Melting point (K) 0.95 (at 25 bar) 24.7 83.6 115.8 161.7 202.2 Enthalpy of vaporization (kJ / mol) 0.08 1.74 6.52 9.05 12.65 18.1 Solubility in water at 20 ° C (cm / kg) 8.61 10.5 33.6 59.4 108.1 230 Atomic number 10 18 36 54 86 Atomic radius (calculated) (pm) 31 38 71 88 108 120 Ionization energy (kJ / mol) 2372 2080 1520 1351 1170 1037 Allen electronegativity 4.16 4.79 3.24 2.97 2.58 2.60
the boiling points of the elements helium neon argon krypton
4.4 27.3 87.4 121.5