Mendeleev

Dmitri Ivanovich Mendeleev was a Russian chemist best known for formulating the periodic law and creating the first widely accepted periodic table of elements. He was born on November 8, 1834, in Tobolsk, Siberia, and studied at Saint Petersburg University. In 1869 he published a table that arranged the known elements by increasing atomic weight and by recurring chemical properties, and he left gaps for elements still to be discovered. The arrangement revealed periodic trends and provided a framework for predicting chemical behavior.

Mendeleev’s most notable contribution was predicting the existence and properties of several undiscovered elements. He coined the term eka-, as in eka-boron, eka-aluminium, and eka-silicon, corresponding to scandium, gallium, and germanium, respectively. When these elements were later discovered and their properties measured, they closely matched his predictions, which bolstered confidence in the periodic law.

Although subsequent work showed that atomic number, rather than atomic weight, is the fundamental organizing principle, the core idea of periodic recurrence of properties remains central to chemistry. The table influenced the development of quantum chemistry and crystallography, and it shaped approaches to chemical education and industrial standards in Russia. Mendeleev also stayed active as a lecturer and researcher at Saint Petersburg University.

His work earned international recognition, and the periodic table remains his most enduring legacy. The element mendelevium (Md, atomic number 101) was named in his honor. Dmitri Mendeleev died on February 2, 1907, in Saint Petersburg.