Definition: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Both alpha and beta decay change the number of protons in an atom's nucleus, thereby changing the atom to a different element. In alpha decay, the nucleus loses two protons. In beta decay, the nucleus either loses a proton or gains a proton. In gamma decay, no change in proton number occurs, so the atom does not become a different element. Answer: protons
Output:
Both alpha and beta decay change the number of what in an atom's nucleus?