Mendeleev arranged the elements in his periodic table primarily according to which physical property?

• A. Atomic number
• B. Density
• C. Atomic mass
• D. Electronegativity

Answer: (C)

Verified step by step guidance

1. Understand that Mendeleev's periodic table was an early attempt to organize elements based on observable properties before the discovery of atomic number.
2. Recall that atomic number is the number of protons in an atom's nucleus, but this concept was not known during Mendeleev's time.
3. Recognize that Mendeleev arranged elements primarily by increasing atomic mass, which was the best measurable property available to him.
4. Note that other properties like density and electronegativity were not the main criteria for his arrangement, although he did consider chemical properties to group similar elements.
5. Conclude that the key physical property Mendeleev used to arrange elements was atomic mass.