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NUCLEAR CHEMISTRY

Understand the different stabilities of radionuclides and their decay rates using integrated rate equations. Learn how to calculate remaining sample amounts and solve for activities in radioactive decay scenarios.

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NUCLEAR CHEMISTRY

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  1. NUCLEAR CHEMISTRY

  2. Rates of Decay & Half Life • Radionuclides have different stabilities and decay at different rates.

  3. Integrated Rate Equation where… • A = the amt. of decaying sample remaining at some time, t • Ao= the amt. of sample present at the beginning • k = rate constant; different for each radionuclide • t = time

  4. Integrated Rate Equation OR… where… • N = # of disintegrations per unit of time; relative activity • No= original activity

  5. HALF-LIFE= the amount of time required for half of the original sample to decay

  6. HALF-LIFE= the amount of time required for half of the original sample to decay Daughter Parent

  7. HALF-LIFE • Half-life = the amount of time required for half of the original sample to decay

  8. Example: Cobalt-60 decays with the emission of beta particles and gamma rays, with a half-life of 5.27 years. How much of a 3.42 g of cobalt-60 remains after 30.0 years? How do you solve for A???

  9. Take the ANTILOG (10x) of both sides.

  10. Example: Cobalt-60 decays with the emission of beta particles and gamma rays, with a half-life of 5.27 years. How much of a 3.42 g of cobalt-60 remains after 30.0 years?

  11. Uses of Radionuclides • Radiocarbon dating: the ages of specimens of organic origin can be estimated by measuring the amount of cabon-14 in a sample.

  12. Carbon Cycle How does C-14 get into living things???

  13. Example: A piece of wood taken from a cave dwelling in New Mexico is found to have a carbon-14 activity (per gram of carbon) only 0.636 times that of wood today. Estimate the age of the wood. (The half-life of carbon-14 is 5730 years.)

  14. Example: A piece of wood taken from a cave dwelling in New Mexico is found to have a carbon-14 activity (per gram of carbon) only 0.636 times that of wood today. Estimate the age of the wood. (The half-life of carbon-14 is 5730 years.) t=3744 yrs = 3740 yrs

  15. Uses of Radionuclides ***NOTE: Objects older than 50,000 years have too little activity to be dated accurately using carbon dating; instead the following methods are used: • Potassium-40 decays to argon-40: half-life = 1.3 x 109 years • Uranium-238 decays to lead-206: half-life = 4.51 x 109 years

  16. Example: A sample of uranium ore is found to contain 4.64 mg of uranium-238 and 1.22 mg of lead-206. Estimate the age of the ore.

  17. Example: A sample of uranium ore is found to contain 4.64 mg of uranium-238 and 1.22 mg of lead-206. Estimate the age of the ore.

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