By what property did Mendeleev arrange the elements in his periodic table?

• A. Increasing atomic number
• B. Alphabetical order
• C. Decreasing density
• D. Increasing atomic mass

Answer: (D)

Verified step by step guidance

1. Understand the historical context: Dmitri Mendeleev created the first widely recognized periodic table in the 19th century before the discovery of the atomic number.
2. Recall that Mendeleev arranged elements based on a property that showed periodic trends and allowed him to predict undiscovered elements.
3. Identify that the property Mendeleev used was the increasing atomic mass of the elements, which was the best available measure at the time.
4. Note that the modern periodic table is arranged by increasing atomic number, but Mendeleev's original table was based on atomic mass.
5. Conclude that the correct property Mendeleev used to arrange elements was increasing atomic mass, not atomic number, alphabetical order, or density.