Question

what quantities vary between isotopes of an element? neutrons and electrons protons, electrons, and atomic number neutrons and atomic mass protons, electrons, an atomic mass

Explanation:

Isotopes of an element have the same number of protons (and electrons, in neutral state) but differ in the number of neutrons. Atomic mass depends on protons and neutrons, so with varying neutrons, atomic mass also varies. Let's analyze options:

• "neutrons and electrons": Electrons are same (neutral), so wrong.
• "protons, electrons, and atomic number": Protons (atomic number) are same for isotopes, wrong.
• "neutrons and atomic mass": Neutrons vary, so atomic mass (sum of protons + neutrons) varies. Correct.
• The last option (partially visible) likely includes protons/electrons which don't vary, so wrong.

Answer:

neutrons and atomic mass