Isotopes of an element differ in
- Athe number of protons
- Bthe mass number
- Cthe number of electrons
- Dthe atomic number
- ENone of the above/More than one of the above
Show answer and explanation
Correct answer: (b) the mass number
Explanation
Isotopes of an element have the same number of protons (same atomic number) but different numbers of neutrons.
The differing neutron count changes the mass number (A), since A = protons + neutrons.
Number of electrons and atomic number (Z) stay the same, so chemical properties are identical.