The correct response is:
the number of protons, electrons, and neutrons.
Since a neutral atom has an equal number of protons and electrons, the atomic number (which represents the number of protons) also indicates the number of electrons. To find the number of neutrons, you can use the atomic weight (usually expressed as a mass number) and subtract the atomic number from it. Thus, you can determine the number of protons, electrons, and neutrons for a neutral atom.