Isotopes are atoms of the same element that have a different number of neutrons. Therefore, isotopes have the following characteristics:
- Isotopes have the same atomic number (same number of protons), but a different atomic mass number (a different number of neutrons).
- Isotopes behave the same chemically, because they are the same element. The only difference is that one is heavier than the other, because of the additional neutrons.
For example, carbon-12 and carbon-14 are both isotopes of carbon. Carbon-12 has 6 neutrons; carbon-14 has 8 neutrons.