Answer:
Different mass, same atomic number
Explanation:
- Elements are made of similar atoms, however the atoms may have different number of neutrons but the same number of protons in their nucleus.
- Such atoms that have equal number of protons but different number of neutrons are known as isotopes.
- Difference in the number of neutrons makes isotopes to have different mass numbers.
- Atomic number is the number of protons in the nucleus of an atom, therefore, isotopes have the same atomic number.
