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

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

Answer: (B)

Verified step by step guidance

1. Understand the historical context: Dmitri Mendeleev created the first widely recognized periodic table in the late 19th century, before the discovery of the atomic number concept.
2. Recall that Mendeleev arranged elements based on their properties and noticed a repeating pattern when elements were ordered by increasing atomic mass.
3. Recognize that Mendeleev's arrangement grouped elements with similar chemical properties into columns, which helped predict the existence and properties of undiscovered elements.
4. Note that the concept of atomic number (number of protons) was not known at Mendeleev's time, so he could not arrange elements by atomic number.
5. Conclude that Mendeleev arranged the elements in his original periodic table by increasing atomic mass, which was the best available method to reveal periodic trends.