How did the discovery of predicted elements support Mendeleev's periodic table?

The discovery of predicted elements, such as gallium and germanium, confirmed Mendeleev's predictions about the existence and properties of these elements. This validation strengthened the credibility of his periodic table by demonstrating that elements could be discovered that fit into the gaps he had left based on chemical properties.

This answer is strong because it directly addresses how the discovery of specific elements supported Mendeleev's work, showcasing the relationship between predictions and empirical evidence. The question tests understanding of the historical development of the periodic table.