Dmitri Mendeleev was a Siberian chemist who was responsible for developing the periodic table of the elements. Born in 1834, he was the youngest of at least 14 children. In the late 1860s he began working on the periodic table of the elements. By arranging all of the 63 elements then known by their atomic weights, he managed to organize them into groups possessing similar properties. When there was no element to fill in a space in the table, he envisioned a new element would one day be found and deduced its properties. Three of those elements were discovered during his lifetime: gallium, scandium, and germanium.