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

• A. By grouping elements with similar colors
• B. By increasing atomic number
• C. By alphabetical order
• D. By increasing atomic mass

Answer: (D)

Verified step by step guidance

1. Understand that Dmitri Mendeleev's original periodic table was an early attempt to organize elements based on their properties before the discovery of atomic number.
2. Recognize that Mendeleev arranged the elements primarily by increasing atomic mass, which was the best available measurable property at the time.
3. Note that by arranging elements in order of increasing atomic mass, Mendeleev observed recurring patterns or periodicity in their chemical properties, leading to the concept of periodicity.
4. Understand that Mendeleev also grouped elements with similar chemical properties into columns (groups), which helped predict the existence and properties of undiscovered elements.
5. Remember that the modern periodic table is arranged by increasing atomic number, but Mendeleev's original table was based on atomic mass, not atomic number or color or alphabetical order.