Atomic number 18 Atomic mass 39.948 g.mol -1 Electronegativity according to Pauling unknown Density 1.78.10 -3 g.cm -3 at 0 °C Melting point -189 °C Boiling point -185.7 °C Vanderwaals radius 0.192 nm Ionic radius unknown Isotopes 6 Electronis shell [Ne] 3s23p6 Energy of first ionisation 1520 kJ.mol -1 Energy of second ionisation 2665.8 kJ.mol […]