PERIODIC TABLE No. Atomic Weight Name Sym. M.P. (°C) B.P. (°C) Density* (g/cm 3 ) Earth crust (%)* Discovery (Year) Group* Electron configuration Ionization energy (eV) 1 1.008 Hydrogen H -259 -253 0.09 0.14 1776 1 1s 1 13.60 2 4.003 Helium He -272 -269 0.18 1895 18 1s 2 24.59 3 6.941 Lithium Li 180 1,347 0.53 1817 1 [He] 2s 1 5.39 4 9.012 Beryllium Be 1,278 2,970 1.85 1797 2 [He] 2s 2 9.32 5 10.811 Boron B 2,300 2,550 2.34 1808 13 [He] 2s 2 2p 1 8.30 6 12.011 Carbon C 3,500 4,827 2.26 0.09 ancient 14 [He] 2s 2 2p 2 11.26 7 14.007 Nitrogen N -210 -196 1.25 1772 15 [He] 2s 2 2p 3 14.53 8 15.999 Oxygen O -218 -183 1.43 46.71 1774 16 [He] 2s 2 2p 4 13.62 9 18.998 Fluorine F -220 -188 1.70 0.03 1886 17 [He] 2s 2 2p 5 17.42 10 20.180 Neon Ne -249 -246 0.90 1898 18 [He] 2s 2 2p 6 21.56 11 22.990 Sodium Na 98 883 0.97 2.75 1807 1 [Ne] 3s 1 5.14 12 24.305 Magnesium Mg 639 1,090 1.74 2.08 1755 2 [Ne] 3s 2 7.65 13 26....