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

16. Example: A sample of uranium ore is found to contain 4
Example: A sample of uranium ore is found to contain 4.64 mg of uranium-238 and 1.22 mg of lead Estimate the age of the ore.