Question

1. what defines isotopes of an element? *

a) different numbers of protons
b) different numbers of neutrons
c) different numbers of electrons
d) different atomic numbers

1. which part of the atom never changes in isotopes? *

a) proton number
b) neutron number
c) mass number
d) atomic mass

Explanation:

1. Isotopes of an element have the same number of protons but different numbers of neutrons. Protons determine the element's identity, and neutrons vary among isotopes.
2. The number of protons in an atom never changes for isotopes. Isotopes are defined by the constancy of proton - number while the neutron - number can vary, changing the mass number and atomic mass.

Answer:

1. B. Different numbers of neutrons
2. A. Proton number