The modern periodic table is arranged by which of the following?

• A. Decreasing density
• B. Alphabetical order of element names
• C. Increasing atomic number
• D. Increasing atomic mass

Answer: (C)

Verified step by step guidance

1. Understand that the modern periodic table is organized based on a fundamental property of elements that reflects their identity.
2. Recall that early versions of the periodic table were arranged by increasing atomic mass, but this arrangement had inconsistencies.
3. Recognize that the modern periodic table is arranged by increasing atomic number, which is the number of protons in an atom's nucleus.
4. Know that arranging elements by increasing atomic number aligns elements with similar chemical properties into groups or families.
5. Conclude that the correct organizing principle of the modern periodic table is increasing atomic number, not density, alphabetical order, or atomic mass.