The Lost Elements: The Periodic Table's Shadow SideThe Periodic Table of Elements hasn't always looked like it does now, a well organized chart arranged by atomic number. In the mid nineteenth century, chemists were of the belief that the elements should be sorted by atomic weight. However, the weights of many elements were calculated incorrectly, and over time it became clear that not only did the elements need rearranging, but that the periodic table contained many gaps and omissions: there were