Mendeleev’s Periodic Table
Mendeleev’s original periodic table included 63 chemical elements. On his table, Mendeleev showed that, when arranged by atomic weight, the elements display a periodicity of properties. The table organized the elements in groups vertically.
Mendeleev’s table had blank spaces as placeholders to represent unknown elements. By following the trends of the table, he was able to determine characteristics of new elements. When the elements were discovered later, Mendeleev’s predictions came true.