Lecture 17 Outline of Last Lecture I. Types of Nuclear Changes II. Chemical vs Nuclear Changes III. Binding Energy IV. Isotopic Stability V. Ionizing Radiation Outline of Current Lecture I. Beta Decay II. Band of Stability III. Worksheet IV. Interpreting the Graph V. Half-Life Questions Current Lecture Beta Decay: - If a problem says beta, assume its negative (or an electron) - There are two types of beta though, a positron (positive beta) and an electron (negative beta) Band of Stability: - The further away something is from the band of stability, the less stable it is and the smaller its half life is - Band of stability plots neutrons vs protons - Isotopes want to get to a stable state so they will go through the process of alpha decay, positron, etc to reach that stable state Worksheet: 1. Write a balanced nuclear equation for the alpha decay of Po-210. 210Po → 4He + 206Pb 2. Experiment involving each student flipping a coin (heads = standing, tails = sitting) CH 302 1st EditionInterpreting the Graph: - Not linear - No constant slope - The first event shows the most Po lost o There was the most Po at this time, so when you have the most to begin with you also have the most to lose - The Po initially and finally is related - As the change in number of Po goes down, the amount of Pb increases by that same amount Half Life Questions: 1. Imagine we started with 96 student isotopes. How many 1⁄2 lives would have to pass to get to 6 student isotopes left? 4 events because… 96/2 =48 48/2 = 24 24/2 = 12 12/2 = 6 2. If you had 960 student isotopes, how many 1⁄2 lives would have to pass to get 60 student isotopes left? 4 events because… 960/2 = 480 480/2 = 240 240/2 = 120 120/2 = 60 3. P-32 has a half-life of 14 days. After 3 months what would be the residual radioactivity of 1 millicurie of ATP labeled with P-32? 15.625 microcuries because 3 months is about 6 half
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