Date context
1834–1907
Organization driven by teaching
Born in Tobolsk, Siberia, Mendeleev studied in St Petersburg and became a chemistry teacher and investigator. Preparing Principles of Chemistry confronted him with the problem of presenting many elements and their properties in a coherent, teachable order.
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The periodic system of 1869
He arranged elements using atomic weights and chemical properties, recognizing recurring patterns and publishing his system in 1869. Meyer and others independently investigated classification. The periodic system emerged through comparison, disagreement and revision, not through an isolated act without predecessors.
Leaving gaps and making predictions
Rather than forcing every position to contain a known element, Mendeleev developed predictions for some missing members. Later discoveries such as gallium, scandium and germanium allowed comparisons with measured properties, helping establish the system as a research tool as well as an organizing scheme.
From historical tables to modern ones
His 1871 table records further development of the arrangement. Modern tables use atomic number, with explanations requiring later work on electronic structure. Mendeleev also worked on industry and metrology, a career extending beyond any one immutable version of the table.