Chem 1120 1st Edition Lecture 10 Outline of Last Lecture I Radioactivity A Chemical vs Nuclear Reactions B Definitions and Review of the nucleus II Equations Terms and Notation III Balancing Nuclear Reactions A Modes of Radioactive Decay Outline of Current Lecture I Nuclear Stability II Radioactive Decay Series a Nuclear Transmutations III Particle Accelerators and their Use IV Rates of Radioactive Decay a Carbon Dating Current Lecture I Patterns of nuclear stability 265 isotopes are stable and they all lie in a belt of stability nuclei with over 83 protons are all radioactive some magic numbers to remember nuclei with 2 8 20 28 50 or 82 protons or neutrons or 126 neutrons are usually more stable even numbers of protons or neutrons are favored These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II So about 80 radioactive isotopes occur naturally If Earth is 4 5 billion years old why have all 80 not all decayed The answer is that radioactive series produce isotopes Each series is fathered by a very long half life isotope The Uranium 238 Decay Series large radioactive nuclei cannot stabilize by undergoing only one nuclear transformation they undergo a series of decays until they form a stable nuclei often a nuclide of lead A nuclear transmutation the induced conversion of one nucleus into another Research into atomic structure led to the discovery of the neutron and the production of artificial radioisotopes later led to high energy bombardment and particle accelerators Over 1000 radioisotopes have been produced In 1933 the first artificial radioisotope was produced by the Curies Example Write the nuclear equation for the following bombardment reactions III In the 1930s particle accelerators were invented to communicate high kinetic energies to particles by placing them in an electric field usually in combination with a magnetic field Major advance linear accelerator which used alternating voltages to change the charges in a series of tubes Cyclotron uses electromagnets to give the particle a spiral path Synchrotron uses a synchronously increasing magnetic field to make the path circular Examples of particle accelerators Stanford Linear Accelerator FermiLab CERN Accelerators can be used for producing isotopes used in medical applications studying the fundamental nature of matter or the synthesis of transuranium elements elements with atomic numbers higher than uranium heaviest naturally occurring element IV Radioactive nuclei decay at a characteristic rate independent of the chemical substance first order kinetic process Example 28 of a sample of Nitrogen 17 decays in 1 97 s What is this isotope s half life in s 1 A Carbon 14 Dating atmospheric CO2 contains a fixed C 14 C 12 ratio photosynthesis results in biochemicals in living plants and animals with this same C 14 C 12 ratio upon death the decaying C 14 is not replenished dead objects have a C 14 C 12 ratio less than that of the atmosphere Carbon 14 has a half life of 5730 years Can be used to date objects up to 36 000 years old for older materials U 238 Pb 208 and K 40 Ar 40 dating is employed Earth s oldest rocks have been dated at 3 8X10 9 years old Earth s age is estimated to be about 4 5X10 9 years old