Periodic Table

The discovery of the individual elements was a necessary prerequisite for the construction of the periodic table. The first pure elements have been known since the time of the Ancient Greeks who used the metallic elements gold (Au), silver (Ag), tin (Sn), copper (Cu), lead (Pb), and mercury (Hg). The first individual credited with the discovery of an element was Hennig Brand, a German scientist who discovered the element phosphorous in 1649. There were 63 known elements in 1869, the year Mendeleev created the periodic table.

Dmitri Ivanovitch Mendeleev (1834-1907) was born in Siberia and studied chemistry at St. Petersburg Institute in Russia. He went on to become a science teacher and later a lecturer and researcher at the University of St. Petersburg. It was through his experience as a teacher that Mendeleev realized a classification system of the known elements was needed. Earlier attempts were made to order the known elements, but they suffered from either being too simplistic or led to inconsistencies that limited their usefulness.

With the purpose of assembling the 63 known elements into an ordered system, Mendeleev wrote the elements' names on individual cards. The cards also contained the atomic mass and specific gravity as well as other known chemical data for that element. By arranging the cards by increasing atomic mass in rows, and then in columns so that elements having similar chemical properties would lie under each other, the first periodic table was formed.