You will be given a definition of a task first, then some input 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: Isotopes have the same number of protons and electrons, but a different number of what? Answer: neutrons
Output:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Isotopes have the same number of protons and electrons, but a different number of neutrons.