24.1 Radioisotopes

Definitions Radioisotope: (short for “radioactive isotope”) an isotope of an atom that emits radiation Half-life: the time it takes for half of a sample of a radioactive isotope to decay

Example If you have 1.00 g of Cesium-137 (half-life of 30 yrs), how much will remain after… 15 yrs?30 yrs? 60 yrs?120 yrs?

Radiocarbon Dating Using carbon-14 to determine the age of a non-living organic substance Can be used to predict the age of human remains, cloth, paper, leather, etc. As living things use carbon (usually in the form of CO 2 ) part of that come from carbon-14 Accurate up to 7000 yrs, approx. up to 30,000 yrs

Types of Radiation and Radioactive Decay Alpha decay –A radioactive isotope breaks down into a stable atom and an alpha particle –Easily stopped, does not pose a health threat

Types of Radiation and Radioactive Decay Beta decay –A radioactive isotope breaks down into a stable atom and a beta particle – In effect, turns a neutron into a proton –can pass through clothing and damage skin

Types of Radiation and Radioactive Decay Gamma decay –Does not consist of particles –Extremely damaging, lead must be used to stop it

Nuclear Bombardment Rxns An atom is bombarded with particles to make the nucleus unstable When using alpha particles, must achieve a high speed, so a long tube is used (“atom smasher”, particle accelerator) Neutron bombardment does not need high speeds Used in medicine to produce radiotracers