The Periodic Table is an essential part of the language of chemistry. It has much in common with a thesaurus, providing a guide to similarities and differences among the elements. From the way elements are organized in the Periodic Table, we can predict their behavior and write chemical formulas of compounds using just a few general guideli nes. Using such rules is not the same as understanding why elements in certain areas the Periodic Table behave as they do, but the trends that arise from the arrangement of elements in the Periodic Table allows a chemist to remember useful facts about the types of compounds formed from specific elements and their chemical reactions.

In the second half of the nineteenth century, data from laboratories in France, England, Germany and Italy were assembled into a pamphlet by Stanislao Cannizzaro, a teacher in what is now northern Italy...