In the context of the periodic table, what does it mean that the relationship among elements is 'periodic'?

• A. All elements have identical chemical properties regardless of their position.
• B. The atomic mass of elements increases in a random pattern across the table.
• C. The properties of elements repeat at regular intervals when arranged by increasing atomic number.
• D. Elements are grouped based solely on their physical state at room temperature.

Answer: (C)

Verified step by step guidance

1. Understand that the term 'periodic' in the periodic table refers to a repeating pattern or cycle.
2. Recognize that elements are arranged in order of increasing atomic number, not atomic mass.
3. Know that as you move across a period (row) in the periodic table, the chemical properties of elements change gradually and then repeat in the next period.
4. This repetition of properties at regular intervals is what defines the periodic law.
5. Therefore, the 'periodic' relationship means that the properties of elements repeat at regular intervals when arranged by increasing atomic number.