Answer : 2. "Mendeleev"
Explanation :

Dmitri Mendeleev, a Russian chemist, is credited with the invention of the modern periodic table. In 1869, Mendeleev arranged the known elements based on their atomic masses and properties, leaving gaps for undiscovered elements. His key insight was to organize the elements in a way that revealed their periodicity, grouping elements with similar properties together. This organization laid the foundation for the periodic law.

Mendeleev's periodic table was a significant breakthrough because it not only systematized the known elements but also predicted the properties of elements yet to be discovered. The subsequent confirmation of these predictions, such as the discovery of gallium and germanium, solidified Mendeleev's contribution to the understanding of the relationships among the elements.