Dmitri+Mendeleev

Mendeleev was responsible for creating the first periodic table of elements. In 1868-1870 Mendeleev created a table that organized the known elements in increasing atomic weight for his book The Principles of Chemistry. His table only had 63 elements. However, when he organized them in horizontal rows he found a pattern, but only if he left blank spaces blank. Here is Mendeleev's first table with the blanks in it.

Mendeleev amazingly would predict that one day the blank spaces would be future elements, and he even prdicted their properties.