Periodic Table of the Elements 1A 8A 1 ? 2010 Todd Helmenstine 2 H About Chemistry He 1.00794 4.002602 Hydrogen 2A 3A 4A 5A 6A 7A Helium 3 4 5 6 7 8 9 10 Li Be B C N O F Ne 6.941 9.012182 10.811 12.0107 14.0067 15.9994 18.9984032 20.1797 Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar 22.989769 24.3050 26.9815386 28.0855 30.973762 32.065 35.453 39.948 Sodium Magnesium 3B 4B 5B 6B 7B 1B 2B Aluminum Silicon Phosphorus Sulfur Chlorine Argon 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.0983 40.078 44.955912 47.867 50.9415 51.9961 54.938045 55.845 58.933195 58.6934 63.546 65.38 69.723 72.64 74.92160 78.96 79.904 83.798