What was Dmitri Mendeleev's greatest contribution to the history of the periodic table?

• A. He introduced the concept of atomic number as the basis for element arrangement.
• B. He discovered the noble gases and added them to the periodic table.
• C. He arranged elements by increasing atomic mass and predicted the existence and properties of undiscovered elements.
• D. He classified elements into metals, nonmetals, and metalloids.

Answer: (C)

Verified step by step guidance

1. Understand the historical context of the periodic table before Mendeleev's work, where elements were known but not systematically organized.
2. Recognize that Dmitri Mendeleev arranged elements in order of increasing atomic mass, which was the best available property at the time for organizing elements.
3. Note that Mendeleev's arrangement revealed periodic patterns in element properties, leading him to group elements with similar chemical behaviors together.
4. Appreciate that Mendeleev predicted the existence and properties of elements that had not yet been discovered, leaving gaps in his table for these elements.
5. Conclude that Mendeleev's greatest contribution was this predictive and systematic organization of elements by atomic mass, which laid the foundation for the modern periodic table.