What is the basic theme of organization in the periodic table?

• A. Elements are classified according to their chemical reactivity.
• B. Elements are grouped based on their physical state at room temperature.
• C. Elements are arranged in order of increasing atomic number.
• D. Elements are organized by their atomic mass.

Answer: (C)

Verified step by step guidance

1. Understand that the periodic table is a systematic arrangement of elements that reveals periodic trends in their properties.
2. Recall that early versions of the periodic table were organized by atomic mass, but this led to inconsistencies in element placement.
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 atomic number aligns elements with similar chemical properties into columns called groups or families.
5. Conclude that the basic theme of organization in the periodic table is the arrangement of elements in order of increasing atomic number, which reflects periodicity in their chemical behavior.