2 This plot shows the nuclides that are known to exist and those that are

2 this plot shows the nuclides that are known to

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This plot shows the nuclides that are known to exist and those that are stable. The stable nuclides are indicated in blue, and the unstable nuclides are indicated in green. Note that all isotopes of elements with atomic numbers greater than 83 are unstable. The solid line is the line where n = Z.29
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30DECAY SERIESin nature, often one radioactive nuclidechanges in another radioactive nuclidedaughter nuclide is also radioactiveall of the radioactive nuclides that are produced one after the other until a stable nuclide is made is called a decay seriesto determine the stable nuclide at the end of the series without writing it all out1.count the number of aand bdecays2.from the mass no. subtract 4 for each adecay3.from the atomic no. subtract 2 for each adecay and add 1 for each b
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FIGURE 21.9: DECAY SERIESUranium-238 undergoes a radioactive decay series consisting of 14 separate steps before producing stable lead-206. This series consists of eight α decays and six β decays.31
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32DETECTING RADIOACTIVITYTo detect something, you need to identify what it doesRadioactive rays can expose light-protected photographic filmUse photographic film to detect its presence – film badges
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33DETECTING RADIOACTIVITYRadioactive rays cause air to become ionizedAn electroscopedetects radiation by its ability to penetrate the flask and ionize the air insideA Geiger-Müller Counterworks by counting electrons generated when Ar gas atoms are ionized by radioactive rays
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FIGURE 21.35Devices such as (a) Geiger counters, (b) scintillators, and (c) dosimeters can be used to measure radiation. (credit c: modification of work by “osaMu”/Wikimedia commons)34
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FIGURE 21.36Different units are used to measure the rate of emission from a radioactive source, the energy that is absorbed from the source, and the amount of damage the absorbed radiation does.35
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36DETECTING RADIOACTIVITYRadioactive rays cause certain chemicals to give off a flash of light when they strike the chemicalA scintillation counteris able to count the number of flashes per minute
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37NATURAL RADIOACTIVITYthere are small amounts of radioactive minerals in the air, ground, and watereven in the food you eat!the radiation you are exposed to from natural sources is called background radiation
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FIGURE 21.37The total annual radiation exposure for a person in the US is about 620 mrem. The various sources and their relative amounts are shown in this bar graph. (source: U.S. Nuclear Regulatory Commission)38
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39RATE OF RADIOACTIVITYit was discovered that the rate of change in the amount of radioactivity was constant and different for each radioactive “isotope”change in radioactivity measured with Geiger countercounts per minuteeach radionuclide had a particular length of time it required to lose half its radioactivity a constant half-lifewe know that processes with a constant half-life follow first order kinetic rate lawsrate of change not affected by temperaturemeans that radioactivity is not a chemical reaction!
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