How was Mendeleev's periodic table originally arranged?

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

Answer: (B)

Verified step by step guidance

1. Understand that Mendeleev's periodic table was an early attempt to organize elements based on their properties before the discovery of atomic number.
2. Recall that Mendeleev arranged elements primarily by increasing atomic mass, which was the best available measurable property at the time.
3. Recognize that this arrangement allowed Mendeleev to group elements with similar chemical properties into columns, predicting the existence and properties of undiscovered elements.
4. Note that the modern periodic table is arranged by increasing atomic number, but Mendeleev's original table was based on atomic mass, not atomic number.
5. Conclude that the correct way Mendeleev originally arranged the periodic table was by increasing atomic mass.