Final answer:
Dmitri Mendeleev, a Russian chemist, developed the periodic table of the elements in 1869. He organized the elements based on their characteristics and made predictions about unknown elements.
Step-by-step explanation:
Dmitri Mendeleev, a Russian chemist, was the person who developed the periodic table of the elements. Mendeleev published his periodic table in 1869, which organized the elements according to their unique characteristics such as atomic number, density, and boiling point. He also made predictions about the existence and properties of then-unknown elements, some of which were later discovered and found to match his predictions.