10 Discoveries In Chemistry By Malachi Roldan Aug 1, 1774 Discovery of Oxygen 1803 Atomic Theory Apr 16, 1808 Electricity Transforms Chemicals Jun 2, 1811 Atoms Combine Into Molecules 1828 Synthesis of Urea 1850 Chemical Structure Apr 1, 1850 Atoms Have Signatures of Light 1860 Periodic Table of the Elements 1890 Radioactivity Oct 2, 1897 The Electron