The Russian chemist Dmitri Mendeleev is credited with creating the first widely recognized periodic table of the elements. In 1869, he arranged the known elements mainly by increasing atomic weight and noticed recurring patterns in their chemical properties.
Mendeleev’s breakthrough was leaving gaps for elements that had not yet been discovered. He predicted the properties of several missing elements, calling them eka-aluminium, eka-boron, and eka-silicon. Their later discoveries as gallium, scandium, and germanium closely matched his forecasts, helping persuade chemists that his periodic law captured a real pattern in nature.
Mendeleev was not the only scientist developing an early periodic system. Julius Lothar Meyer produced an important contemporary arrangement, while earlier researchers such as John Newlands and Alexandre-Émile Béguyer de Chancourtois identified partial periodic patterns. Mendeleev’s table became the most influential because it combined organization with successful predictions.
The modern table is ordered by atomic number rather than atomic weight, a change made possible by 20th-century discoveries about atomic structure. Even so, Mendeleev’s 1869 system remains the foundation of the periodic table used today.