How did Dmitri Mendeleev arrange the elements in his original attempt at the periodic table?

• A. By increasing atomic mass
• B. By alphabetical order
• C. By increasing atomic number
• D. By chemical reactivity

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 was known and measurable at the time, which was the atomic mass (also called atomic weight).
3. Recognize that Mendeleev noticed patterns in the properties of elements when they were ordered by increasing atomic mass, which allowed him to predict the existence and properties of undiscovered elements.
4. Note that the concept of atomic number (number of protons) was not known during Mendeleev's time, so he could not have arranged elements by atomic number.
5. Conclude that Mendeleev's original periodic table was arranged by increasing atomic mass, not by alphabetical order or chemical reactivity.