CHEM 1120 Edition 1nd Lecture 9 Outline of Last Lecture I Catalysis a Catalyst b Homogeneous vs Heterogeneous catalysis c Enzymes II Intro to Chapter 21 Nuclear Chemistry a Chemical vs Nuclear Reactions III Radioactivity a Types of Emissions b Balancing Nuclear Equations Outline of Current Lecture I Balancing II Patterns of Nuclear stability a Radioactive decay series b Additional trends III Nuclear Transmutations a Particle Accelerators IV Rates of Radioactive Decay a Decay rate A Change in N Change in t kN b Carbon 14 dating Current Lecture I Balancing a Must balance top numbers and bottom numbers on each side b Use the building blocks that are common to us 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 III IV Patterns of Nuclear Stability a Only 265 isotopes are stable lie in Belt of Stability b Nuclei with 83 protons are radioactive c Magic numbers nuclei with 126 neutrons are usually more stable d Nuclear stability i Radioactive decay predictable ii Above the belt of stability too many neutrons N Z 1 1 Loss of electron iii Below the belt of stability too many protons N Z 1 1 Loss of a positron or gain of electron iv Nuclei with 83 protons always unstable 1 Alpha emission loss of He isotope e Radioactive Decay series i 80 radioactive isotopes occur naturally why aren t they all totally decayed 1 Radioactive series produce isotopes each series is fathered by a very long half life isotope f Additional trends i Magic numbers certain numbers of protons and neutrons tend to be more stable than others ii Nuclei with an even number of protons and neutrons tend to be more stable Nuclear Transmutations a Nuclear transmutation induced conversion of one nucleus into another b Over 100 radioisotopes have been produced i First artificial radioisotope produced by Curies ii Al foil bombarded with alpha particles iii Reactant nucleus Particle in particle out product nucleus shorthand notation c Particle Accelerators i Impart high kinetic energies to particles by placing them in an electric field usually in combination with a magnetic field 1 Linear accelerator used alternating voltages to change the charges in a series of tubes 2 Cyclotron uses electromagnets to give particle spiral path 3 Synchrotron synchronously increasing magnetic field to make the path circular ii Can be miles huge 2 miles long 10 square miles 17 miles long etc iii Applications produce radioisotopes studying nature of matter Rates of Radioactive decay a Radioactive nuclei decay at a characteristic rate independent of the chemical substance first order kinetic process b Decay rate A Change in N Change in t kN i K decay constant ii N number of radioactive nuclei iii Activity A iv Specific activity decay rate g v Becquerel one nuclear disintegration per second vi Curie 3 7 x 10 10 disintegrations per second d s c T1 2 693 k d Ln Nt No kt e Disinteg measured in nuclides f Carbon 14 dating i Atmospheric CO2 contians a fixed C 14 C 12 ratio ii Photosynthesis results in biochemical with this same ratio iii Upon death the decaying C 14 is not replenished iv Dead objects have a C 14 C 12 ratio less than that of the atmosphere v Carbon 14 has a half life of 5730 years vi Can be used to date objects up to 36000 years old vii For older materials U 238 Pb 208 dating is employed V