A radioactive isotope is a variant of a chemical element that has an unstable nucleus and emits radiation as it decays. This process can result in the release of particles or electromagnetic waves, which can be harnessed for various applications, including medical imaging and cancer treatment. Common examples include Carbon-14 and Uranium-238. These isotopes are crucial in fields such as archaeology, where Carbon-14 dating helps determine the age of ancient artifacts. Additionally, radioactive isotopes play a significant role in energy production, particularly in nuclear reactors, where Uranium-235 is used as fuel to generate electricity.