Periodic Table Mendeleev Element Simple Substance Isotopes

One creative way to teach the periodic table is to become better informed on the subject.  In recent years the field of philosophy of chemistry has developed and has examined the nature of the periodic table in great detail.  One of the central topics, not surprisingly has been the question of the nature of the elements.  It turns out that the term element is used rather confusingly in two senses in the English language.  First of all it is used to mean Lavoisier’s simple substances, meaning the last stage of chemical analysis.  A substance that cannot be spit into any further basic components.  The second sense of element is more subtle and at the same time more fundamental.  It is the basic ingredient in every simple substance that survives when a simple substance enters into chemical combination.  For example it is the sodium present in sodium chloride.  This sense of element is sometimes termed ‘element as basic substance’ to distinguish it from Lavoisier’s.  Contemporary philosophers of chemistry are somewhat divided as to the precise way in which these more abstract ‘elements’ should be regarded.  The articles make fascinating reading and can only enrich the knowledge of chemistry instructors.

Returning to the nature of elements, it emerges that the periodic table is a classification of the more abstract sense of element than elements as simple substances.  A simple way to appreciate this is to consider the allotropes of any element like carbon.  When one points to the symbol C in the periodic table, this is taken to mean carbon in the abstract sense and not any one of the three allotropes of the ‘element’.  The same is true of isotopes.  Although many elements occur in various isotopic forms, the periodic table embodies one abstract isotope rather than displaying all the isotopes of an element.  The notion that the periodic table predominantly classifies the elements as basic substances goes back to the discoverer of the periodic system, Dimitri Mendeleev who emphasized this point in many of his books and articles.  For background information on this and other aspects of the periodic table see,