Whose work led to the modern periodic table of elements?

Russian chemist Dmitri Mendeleev published his periodic table in 1869. He organized the known elements by atomic weight and chemical behavior, leaving gaps where he believed undiscovered elements belonged. His predictions were later confirmed, which gave the table enormous credibility. The modern periodic table is now ordered by atomic number rather than atomic weight, but Mendeleev’s pattern remains fundamental. His work changed chemistry from a collection of facts into an organized science.