The Discovery of the Elements in the Periodic Table

Abstract

The 150th anniversary of the publication of The Principles of Chemistry by Mendeleev has been declared “The International Year of the Periodic Table” by the United Nations and is being marked by a multitude of events around the world. There is no doubt that the Periodic Table occupies an iconic position not only for chemistry but more generally as a symbol of scientific endeavour. The proposal of a Periodic Table could not have happened without an understanding of what is required for a substance to be defined as a chemical element and the discovery of sufficient elements to provide a reasonably large sample to attempt to find an ordered pattern. This chapter traces how the first metals were discovered approximately 7,000 years ago and proved to be sufficiently useful to initiate the copper, bronze and iron ages. This journey initially was based on practical considerations but eventually developed into recognised methods of careful and controlled experimentation, observation and theoretical thinking which we now associate with the Scientific Revolution. The practical and conceptual progress made internationally resulted in the discovery and purification of 98 elements which occur naturally on earth and organised them in a logical order in a Periodic Table, which is recognisable by chemists throughout the world. Furthermore, an understanding of the fundamental nature of elements in terms of atoms, whose properties are governed by quantum mechanical principles, led to the synthesis and characterisation of elements not found on earth. Indeed, one in six of the elements in the current Periodic Table is man-made and were made in high technology laboratories since 1940.