Looking Backwards and Forwards at the Development of the Periodic Table

Abstract Since the periodic table has reached the ripe old age of 150 years it may be an appropriate time to look back at the development of this unique scientific icon. It is also an opportunity to look forwards to any changes that the periodic table may undergo in view of the ever-growing list of new elements that continue to be synthesized. The way that the past and future will be examined in this article will be to follow a main thread that focuses on the number of columns in the periodic table at various stages in its development.