Isotopes are different forms of an element that possess the same number of protons but different numbers of neutrons. This variation in neutron count results in different atomic masses for isotopes of the same element. For example, carbon-12 has 6 protons and 6 neutrons, while carbon-14 has 6 protons and 8 neutrons.

Isotopes play a vital role in understanding nuclear structure and stability. The number of neutrons in an isotope affects its stability, and certain isotopes exhibit radioactivity due to an imbalance between the protons and neutrons in their nuclei.

One common application of isotopes is in radiometric dating. By measuring the ratio of certain isotopes in organic materials, scientists can determine the age of fossils or artifacts. For instance, carbon-14 dating is used to estimate the age of ancient artifacts up to around 50,000 years old.

Moreover, isotopes find extensive use in nuclear power. Uranium-235, for instance, is a fissile isotope that can undergo nuclear fission, releasing a tremendous amount of energy. This process forms the basis of nuclear reactors, where controlled fission reactions generate heat to produce electricity.