Uses
Stable Isotopes
Because stable isotopes have similar chemical and physical properties, they have few uses. With some effort they can be separated, but there is usually not a compelling reason to do so. For example, C-12 and C-13 are stable isotopes but because they are similar they don't have specific uses.
The exception is Hydrogen. Hydrogen has the lowest mass of all elements. Therefore any changes in the number of neutrons results in a proportionally large change in mass. The large change in mass influences Hydrogen's chemical and physical properties more than heavier elements.
Radioisotopes (Radioactive Isotopes)
Radioisotopes are unstable and emit radiation when they undergo nuclear decay. Because of this certain isotopes are used as tracers or a source of energy.
Tracers: radiation from isotopes can pass through substances, including body tissues. For example, attaching a tracer to a molecule that binds to certain cancer cells can help diagnose the location of the cancer. Radiation emitted from the radioisotope can be detected with a scanner. For PET scans the isotope used is usually Fluorine-19. Tracers are also used to study chemical reactions and biological processes.
Medical: In addition to being used as tracers for diagnosis, radioactive isotopes (often Strontium-89 and Samarium-153) can be used in the treatment of diseases like cancer.
Radioactive Dating: the age of substances can be determined by measuring the relative abundance of isotopes in a sample. Carbon-14 is frequently used for this purpose.
Nuclear Power: energy from radiation emitted as isotopes undergo decay can be used to generate electricity (often Uranium-233 and 235). Irradiation of Food: radiation from isotopes (e.g., Iodine-131, Cobalt-60 or Cesium-137) can be used to control bacteria or invasive pests on foods. Note this does not make the food radioactive.
Irradiation of Food: radiation from isotopes (e.g., Iodine-131, Cobalt-60 or Cesium-137) can be used to control bacteria or invasive pests on foods. Note this does not make the food radioactive.