How did Dmitri Mendeleev arrange the elements in his first periodic table?

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

Answer: (D)

Verified step by step guidance

1. Understand the historical context: Dmitri Mendeleev created the first periodic table in the 19th century to organize known elements in a meaningful way.
2. Recognize that Mendeleev arranged elements primarily based on their increasing atomic mass, which was the best available property at the time to show periodic trends.
3. Note that Mendeleev's arrangement also grouped elements with similar chemical properties into columns, highlighting periodicity in element behavior.
4. Be aware that the modern periodic table arranges elements by increasing atomic number, but Mendeleev's original table used atomic mass because atomic numbers were not yet discovered.
5. Conclude that the correct way Mendeleev arranged elements was by increasing atomic mass, not by alphabetical order, chemical reactivity, or atomic number.