In today’s periodic table, 118 elements stand side by side, neatly arranged in rows and columns, mapping out their relative size, proudly sharing their family’s traits, and showcasing their relative reactivity and predicted behaviour in different situations. Back in 1869 when Dmitri Mendeleev devised the arrangement of elements we use to this day, there were notable gaps left for elements that had not yet been discovered. As the arrangement of the elements was based on a range of physical and chemical properties, it was easy to predict some of the properties of the missing elements. It was in these gaps that both scientists and artists alike dared to dream about elemental discoveries with both predicted and unpredicted properties. Comic book and science fiction writers in particular had fun postulating some of the possible elements that would give their superheroes the characteristics they required to carry out their tasks. They created fictional elements in place of some of the as yet undiscovered elements, many of which now share properties with elements that exist today.