Question

1. which of the following explains why atoms of the same element can have different mass numbers? they have different numbers of protons they have different numbers of neutrons they have different numbers of electrons they have different numbers of energy levels

Explanation:

Atoms of the same element have the same number of protons. Isotopes of an element have different numbers of neutrons, which causes them to have different masses. Electrons and energy - levels do not affect the mass of an atom in the context of this question.

Answer:

They have different numbers of neutrons