Which feature of Mendeleev's periodic table made his theory about the organization of matter especially powerful?

• A. He grouped elements based solely on their physical appearance.
• B. He arranged elements strictly by increasing atomic mass without exceptions.
• C. He left gaps for undiscovered elements and predicted their properties.
• D. He classified elements according to their chemical reactivity with water.

Answer: (C)

Verified step by step guidance

1. Understand that Mendeleev's periodic table was an early attempt to organize elements based on their properties and atomic masses.
2. Recognize that while many elements were arranged in order of increasing atomic mass, Mendeleev noticed some inconsistencies and chose to prioritize chemical properties over strict atomic mass order.
3. Note that Mendeleev left intentional gaps in his table where no known elements fit the pattern, predicting that these gaps represented undiscovered elements.
4. Appreciate that Mendeleev went further by predicting the properties of these missing elements based on the trends in his table, which was a powerful demonstration of the predictive power of his organization.
5. Conclude that this ability to predict undiscovered elements and their properties made Mendeleev's periodic table especially powerful and influential in the development of the modern periodic table.