The Periodic System An Overview

FIGURE 1.1 The five Platonic solids. O. Benfey,Precursors and Cocursors of the Mendeleev Table The Pythagorean Spirit in Element Classification, Bulletin for the History of Chemistry, 13—14, 60—66, 1992—1993, figure on p. 60 (by permission). 

The earliest understanding of the term element among the Greek philosophers was of a tendency or potentiality that gave rise to the observable properties of the element. This rather subtle distinction between the abstract form of an element and its observable form has been all but forgotten in modem times. It has nonetheless served as a fundamental guiding principle to such noted contributors to the periodic system as Dimitri Mendeleev, its major discoverer. 

Jimpirt futtnt F r , per. Martganefe, Mercure. Molybdene, Nickel, Or. 

FIGURE 1.2 List of 33 simple substances compiled by Lavoisier. Traite Elementaire de Chimie, Cuchet, Paris, 1789, p. 192 

The story of the discovery of the elements is a fascinating one and has been the subject of at least one classic account. A time line for the discoveries is given in table 1.1. This story is not systematically addressed in the present book, although references to predictions and discovery of elements are made throughout. 

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