Greatest Discoveries of Chemistry / Alexandria Arvizu By Malachi Roldan Aug 1, 1774 The Element Oxygen (Discovered) Jan 1, 1803 The Atomic theory Jan 1, 1807 Electricity Transforms Chemicals Jan 1, 1808 Molecules Jan 1, 1838 Synthesis of Urea Jan 1, 1869 Periodic Table Jan 1, 1890 Chemical Structure Jan 1, 1896 Radioactivity Jan 1, 1897 Electrons Jan 1, 1907 Plastics