Final answer:
Mendeleev's periodic table differed from previous tables in that it was arranged by increasing atomic mass with grouping based on properties, included gaps for undiscovered elements, and predicted new elements.
Step-by-step explanation:
Three Ways Mendeleev's Periodic Table was Different
Dmitri Mendeleev's periodic table was innovative in several ways compared to prior versions of the table. Firstly, Mendeleev arranged elements by increasing atomic mass and grouped them by their chemical and physical properties, which was a novel approach at the time. Secondly, Mendeleev's periodic table included intentional gaps for undiscovered elements, predicting their existence and properties. He left blanks at atomic masses 44, 68, 72, and 100, which correspond to scandium, gallium, germanium, and technetium, all of which were later discovered. Lastly, Mendeleev used his table to predict the existence of elements similar to aluminum and silicon, which was a bold move that showed his deep understanding of elemental properties and relationships. The discoveries of gallium and germanium validated his predictions and supported the accuracy of Mendeleev's periodic table.