Periodic table of the elements
The periodic table of the elements is a diagrammatic tool to illustrate the scientific theory of periodicity in chemistry, in which the elements have similar properties based on their position on the table. For example, the elements on the left of the table are all metals. The table has a lot of predictive power, although there are many exceptions to the periodic properities.
The periodic table was first developed by Russian chemist Dimitri Mendeleev. Its layout accurately arranges elements by their electron configuration, atomic number, and chemical properties. Using the structure he created, Mendeleev predicted the existance and properties of several yet-undiscovered elements; when those elements were discovered, his estimates proved to be quite accurate.
