Define and discuss decay half life of isotopes. Indicate the half life of radium, uranium, and carbon. Determine that the half life of isotopes is not affected by temperature, pressure, electric fields or magnetic fields. Discuss how half life is used to determine the age of carbon containing hydrocarbons. Discuss uses for radioactive isotopes in diagnosis and treatment of disease. Discuss the use of iodine radioisotopes for treatment of thyroid disorders.