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• History of the periodic law
• Words to Know
• The modern periodic table
• Recent and future research

The periodic table is a chart that shows the chemical elements and their relationship to each other. The periodic table is a graphic way of representing the periodic law.

History of the periodic law

By the middle of the nineteenth century, about 50 chemical elements were known. One of the questions chemists were asking about those elements was the following: Is every element entirely different from every other element? Or are some elements related to other elements in some way? Are there patterns among the elements?

A number of chemists suggested various patterns. German chemist Johann Wolfgang Döbereiner...