How Many Elements Are in the Periodic Table?

Russian scientist Dmitri Mendeleev is usually credited with the first known publication of a periodic table of elements, in 1869. He created the table by arranging known elements into rows and columns based on atomic weight and the similarity between elements. Using this method, he was also able to predict the existence of heretofore unknown elements, such as Gallium and Germanium. The standard periodic table style in use today is attributed to Horace Deming, an American scientist.