Question

multiple - choice question
the relationship between elements and atomic weight was found to be...
periodic.
erratic.
unrelated.
completely predictable.

Explanation:

The periodic table organizes elements based on their atomic weight (now more accurately atomic number, but historically atomic weight was the basis). The properties of elements repeat periodically as atomic weight increases. "Erratic" (unpredictable), "unrelated", and "completely predictable" (too absolute as there are trends but not everything is completely predictable in a simple sense) are incorrect.

Answer:

periodic.