Why is atomic number considered a better basis than atomic mass for organizing the elements in the periodic table?

• A. Atomic mass directly determines the electron configuration of an element.
• B. Atomic number is less affected by experimental errors than atomic mass.
• C. Atomic mass is always a whole number and does not change for isotopes.
• D. Atomic number reflects the number of protons, which determines the chemical properties of an element.

Answer: (D)

Verified step by step guidance

1. Understand that the atomic number (Z) represents the number of protons in the nucleus of an atom, which uniquely identifies an element.
2. Recognize that the chemical properties of an element are primarily determined by its electron configuration, which depends directly on the number of protons (atomic number) because it dictates the number of electrons in a neutral atom.
3. Note that atomic mass varies due to the presence of isotopes—atoms of the same element with different numbers of neutrons—so atomic mass is not unique to a single element.
4. Realize that organizing elements by atomic mass can lead to inconsistencies because some elements have isotopes with different masses, and the order may not reflect their chemical behavior accurately.
5. Conclude that the atomic number is a better basis for organizing the periodic table because it directly correlates with the element's identity and chemical properties, providing a consistent and logical arrangement.