Which property did Dmitri Mendeleev primarily use to organize the elements in his original periodic table?

• A. Atomic mass
• B. Density
• C. Electronegativity
• D. Atomic number

Answer: (A)

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 a repeating pattern of chemical properties, which helped him predict undiscovered elements.
3. Identify the property Mendeleev used: he primarily organized elements by increasing atomic mass, noticing periodic trends in their chemical behavior.
4. Recognize that atomic number was not known at Mendeleev's time, so it could not have been used for his original arrangement.
5. Conclude that the correct property Mendeleev used to organize the elements in his original periodic table is atomic mass.