Mendeleïev

Dmitri Ivanovich Mendeleev, sometimes spelled Mendeleïev, was a Russian chemist born in 1834 in Tobolsk, Siberia. He studied at the University of Saint Petersburg and later taught and conducted research there. Mendeleev is best known for formulating the Periodic Law and creating the first comprehensive, widely used periodic table of elements. He played a key role in establishing chemistry as a predictive science.

In 1869, Mendeleev published a periodic table that arranged elements by increasing atomic weight and by recurring chemical properties. He left gaps where he believed undiscovered elements would fit, arguing that the table revealed periodic trends rather than a random assortment. He also used these gaps to predict the existence and properties of several yet-undiscovered elements. Among his notable predictions are eka-aluminum (later identified as gallium), eka-silicon (germanium), and eka-boron (scandium), which helped validate the usefulness of the periodic approach.

Mendeleev’s work influenced chemical education and the organization of chemical knowledge for decades. Although later refinements shifted the rationale from atomic weight to atomic number, his periodic framework established a lasting structure for understanding element behavior and guided the search for new elements. He held academic positions in Saint Petersburg and was elected to the Russian Academy of Sciences. He died in Saint Petersburg in 1907, leaving a legacy as a foundational figure in modern chemistry.