Which of the following best explains how elements are arranged on the modern periodic table?

• A. Elements are arranged in order of increasing atomic mass.
• B. Elements are placed based on the number of neutrons in their nuclei.
• C. Elements are grouped according to their chemical reactivity.
• D. Elements are arranged in order of increasing atomic number.

Answer: (D)

Verified step by step guidance

1. Understand that the modern periodic table is organized based on a fundamental property of elements called the atomic number, which is the number of protons in an atom's nucleus.
2. Recall that earlier versions of the periodic table arranged elements by increasing atomic mass, but this caused inconsistencies in element properties and their placement.
3. Recognize that the atomic number uniquely identifies each element and determines its chemical behavior, making it the most logical basis for arrangement.
4. Note that elements with similar chemical properties are grouped together in columns (called groups or families) because they have the same number of valence electrons, which is related to their atomic number.
5. Conclude that the best explanation for the arrangement of elements on the modern periodic table is that they are ordered by increasing atomic number, not by atomic mass, neutron number, or solely chemical reactivity.