Whose periodic table organized the elements?

The periodic table of the elements, one of the most important tools in science, was devised by the Russian chemist Dmitri Mendeleev in 1869. He arranged the known chemical elements in order of increasing atomic weight and grouped those with similar chemical properties into columns, revealing a repeating, or periodic, pattern. His genius lay in leaving gaps for elements that had not yet been discovered and confidently predicting their properties; when elements such as gallium and germanium were later found and matched his predictions, his table was triumphantly vindicated. The modern periodic table arranges elements by atomic number rather than weight, a refinement made after the discovery of the proton. Today it organises all 118 known elements and remains a cornerstone of chemistry, guiding scientists in understanding how substances behave and combine.