Which properties of gallium was Mendeleev able to predict before its discovery?

• A. Its magnetic properties and boiling point
• B. Its color and electrical conductivity
• C. Its atomic mass, density, and melting point
• D. Its crystal structure and radioactivity

Answer: (C)

Verified step by step guidance

1. Understand that Dmitri Mendeleev created the periodic table by arranging elements according to increasing atomic mass and noticed periodic trends in their properties.
2. Recognize that Mendeleev left gaps in his periodic table for elements that were not yet discovered, predicting their properties based on the trends of neighboring elements.
3. For gallium, which Mendeleev predicted before its discovery, he estimated properties such as atomic mass, density, and melting point by comparing it to elements in the same group and period.
4. Note that Mendeleev did not predict properties like magnetic behavior, color, electrical conductivity, crystal structure, or radioactivity, as these were either less understood or not part of his predictive approach.
5. Therefore, the properties Mendeleev predicted for gallium were its atomic mass, density, and melting point, based on periodic trends and the position of gallium in the periodic table.