On the Periodic System

The publication of this special issue is a special pleasure for me since I have been carrying out research on the periodic system of the elements for some years. Whereas many readers may have first become intrigued by chemistry after seeing some striking demonstration in their childhood, or by playing around with a chemistry set, others like myself may have been taken by the elegance and complexity of the periodic system. The periodic table is perhaps the most powerful icon of chemistry, because it seems to contain the whole subject within one single chart. Nobody who delights in classification and orderliness can fail to be struck by the beauty and the simplicity of the chemist’s periodic system. Even people who have long ceased to study chemistry can usually dimly recall the periodic table from their school days, although everything else may have been forgotten. I believe that the periodic system lies at the heart of philosophy of chemistry which, among other things, seeks to clarify the ‘big picture’ concerning the nature of chemistry. It seems rather obvious that if one is seeking an overall view of chemistry one should focus on that which provides the ‘big picture’ even within chemistry itself, namely the periodic system. As is well known, the periodic system has matured and has been modified in specific ways over its 130-year history since the date of its ‘official discovery’ by Mendeleev in 1869. But it has also remained essentially unchanged in expressing the approximate repetition in the properties of the elements after certain regular but varying intervals have been crossed. The periodic system stands as a major challenge to the view that chemistry has been reduced to quantum mechanics. Indeed, it seems odd in some ways to think