How was the first periodic table, created by Dmitri Mendeleev, primarily arranged?

• A. By electron configuration
• B. By increasing atomic number
• C. By chemical reactivity
• D. By increasing atomic mass

Answer: (D)

Verified step by step guidance

1. Understand that Dmitri Mendeleev's first periodic table was created before the discovery of the atomic number and electron configurations.
2. Recognize that Mendeleev arranged elements primarily based on their increasing atomic mass, which was the best available property at the time to organize elements.
3. Note that Mendeleev also grouped elements with similar chemical properties into columns, which helped predict the existence and properties of undiscovered elements.
4. Realize 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 primary arrangement principle of Mendeleev's periodic table was by increasing atomic mass, not by electron configuration, atomic number, or chemical reactivity alone.