Question

atoms of the same element that have different mass numbers are called...
select one:
a. isotopes.
b. alpha particles.
c. beta particles.
d. ions.

Explanation:

Isotopes are defined as atoms of the same element (same atomic number, meaning same number of protons) that have different mass numbers due to varying numbers of neutrons. Alpha particles are helium nuclei, beta particles are high-energy electrons/positrons, and ions are charged atoms/molecules from electron gain/loss, so these do not match the given definition.

Answer:

a. isotopes.