Module 46 -- Rate of Radioactive Decay and Half Life.ppt -...

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24-1Units of RadioactivityThe SI unit of radioactivity is thebecquerel(Bq),defined as one disintegration per second (d/s).Thecurie(Ci) is a more commonly used unit:1 Ci = 3.70x1010d/s
24-2Rate of Radioactive DecayRadioactive nuclei decay at a characteristic rate,regardless of the chemical substance in which they occur.The rate of radioactive decay (A) (also called the activity)is proportional to the number of nuclei present (thenumber decaying per unit time is proportional to thenumber present)A=kNkis called thedecay constantand is characteristic ofeach type of nuclide. The larger the value ofk, the higheris the decay rate, or thehigherthe activity of thesubstance.
24-3Half-Life of Radioactive DecayThehalf-lifeof a nuclide is the time taken for half thenuclei in a sample to decay.- The number of nuclei remaining is halved after each half-life.- The mass of the parent nuclide decreases while the mass ofthe daughter nuclide increases- Activity is halved with each succeeding half-life.
24-4Figure 24.6Decrease in the number of14C nuclei over time.

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Term
Spring
Professor
DR.JOHANSON
Tags
Radioactive Decay, rate of radioactive decay

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