Which feature distinguished Mendeleev's periodic table from other early arrangements of the elements?

• A. He organized elements alphabetically by their names.
• B. He grouped elements solely by their physical state (solid, liquid, gas).
• C. He arranged elements by increasing atomic mass and left gaps for undiscovered elements.
• D. He classified elements based on their color.

Answer: (C)

Verified step by step guidance

1. Understand the historical context: Early attempts to organize elements were based on various properties such as alphabetical order, physical state, or color, but these methods did not reveal clear periodic trends.
2. Recognize Mendeleev's key innovation: He arranged elements in order of increasing atomic mass, which was a more systematic approach than previous methods.
3. Note that Mendeleev left intentional gaps in his table where no known elements fit the pattern, predicting the existence and properties of undiscovered elements.
4. Understand that this predictive power and organization by atomic mass distinguished Mendeleev's periodic table from other early arrangements.
5. Summarize that Mendeleev's periodic table was unique because it combined increasing atomic mass with the prediction of new elements, rather than organizing elements alphabetically, by physical state, or by color.