Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This difference in neutron count results in varying atomic masses. For example, the element Carbon has isotopes like Carbon-12 and Carbon-14, which are used in various applications, including radiocarbon dating. The stability of isotopes can vary; some are stable, while others are radioactive and decay over time. Radioactive isotopes, such as Uranium-238, are crucial in fields like nuclear energy and medicine, where they are used in imaging and treatment processes.