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Nuclear Chemistry Objective: To explain the process of radioactive decay using nuclear equations and half life Essential Question: How do unstable (radioactive) isotopes become stable? Review: Radioactivity introduction Radioactivity video – 4 minutes http://ed.ted.com/lessons/radioactivity-expect-theunexpected-steve-weatherall Review questions: http://ed.ted.com/lessons/radioactivity-expect-theunexpected-steve-weatherall#review Dig deeper: http://ed.ted.com/lessons/radioactivity-expect-theunexpected-steve-weatherall#digdeeper Review: Radioactive Isotopes A radioactive isotope has an unstable nucleus that undergoes spontaneous changes. - Emits particles - - - 1. 2. Emits energy in the form of __________ waves. Transmutates into another element Types of Radiation Alpha Decay Beta decay Gamma Decay Particles emitted from a radioactive isotope Type Symbol Next slide Charge Mass Rad.Strength Radiation Strength: Explain in your notes how each of the radioactive emissions are blocked. Which is the most damaging (strongest)? Strong Nuclear Force: Holds the nucleus together Limit to the # neutrons: A nucleus with too many neutrons will be unstable and change Balancing Nuclear Reactions Keep track of atomic number (Z) and mass number (A): protons & neutrons Totals of A & Z must be the same before and after the reaction. Shown by “Before” “ After” Nuclear reactions Total number of atomic numbers and the total mass numbers must be equal on both sides of the equation. Examples: Nuclear Equations 1. 2. 3. 4. 27 4 He ---> 30 P + ? Al + 13 2 15 238 U 234 Th + ? 92 90 14 C 0 e + ? 6 -1 239 Pu + 4 He 242 Cm + ? 94 2 96 Nuclear Equations Practice Website Nuclear Reactions Emission of Alpha or Beta particles http://phet.colorado.edu/en/simulation/betadecay http://phet.colorado.edu/en/simulation/alphadecay Radioactive decay No two radioactive isotopes decay at the same rate. Therefore, decay rate can be used to identify the isotope. Decay is measured by half life. Half-life Measure of Radioactive decay rate. Measured as the time it takes for ½ of a sample of radioisotope’s nuclei to decay into its products. Half Life Decay of a radioisotope Number of Elapsed time Half-Lives 0 0 Amount remaining 100 g 1 1.5 year 50 g 2 3 years 25 g 3 4.5 years 12.5 g Examples of the Half Life of Radioactive Elements Tearing Through a Half Life 800 Billion Bismuth-210 Atoms Time (years) Half Life: http://phet.colorado.edu/en/simulation/radioac tive-dating-game Number of radioactive isotopes Number of years Fission and Fusion http://phet.colorado.edu/en/simulation/nuclear -fission