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NUCLEAR CHEMISTRY

This text explores the principles of nuclear chemistry, specifically focusing on the rates of decay and half-life of various radionuclides. It introduces integrated rate equations for decay calculations, emphasizes the significance of half-life in understanding stability, and provides practical examples, such as the decay of Cobalt-60 and Carbon-14 dating techniques. Additionally, it discusses methods for estimating the age of ancient specimens and estimates the age of uranium ore. This foundational knowledge is crucial for applications in fields like archaeology and geology.

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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. 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.)

  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.) t=3744 yrs = 3740 yrs

  14. 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

  15. 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.

  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.

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