You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Question: What term refers to a list of the elements that will replace the ones below them in single-replacement reactions? Answer: activity series
Solution: A list called the activity series does the same thing the periodic table does for halogens: it lists the elements that will replace elements below them in single-replacement reactions.
Why? This is a valid supporting statement since it connects both the answers and question to generate the supporting fact

New input: Question: What substance can be identified by their atomic number and mass number? Answer: elements
Solution:
Elements can be identified by their atomic number and mass number.