Question

Isotopes of the same element have different ____
a. numbers of neutrons
b. numbers of protons
c. numbers of electrons
d. atomic numbers

Answer 1

neutrons

Answer 2

Neutron, thats why they are isotopes. They are the same element with the same mass but different properties due to the difference of neutrons in the nucleus. Therefore it gives them different chemical properties. So you have to differentiate them otherwise you wouldn't be able to mark the difference of an atom of same mass that would give different results