1. The ABG's (or Alpha, Beta, Gamma) of Radioactivity
Friday, September 22nd, 2017

2. What do we mean by Radioactivity?
Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves.
There are numerous types of radioactive decay. The general idea:
An unstable nucleus releases energy to become more stable

4. Three Common Types of Radioactive Emissions
Alpha
Beta
Gamma

5. Radioactive Isotopes
Radioactive elements are unstable. They decay, and change into different elements over time.
Not all elements are radioactive. Those that are listed below are the most useful for geologic dating of fossils are:
U-238 Half-life = 4.5 Billion Years
K-40 Half-life = 1.25 Billion Years
C-14 Half-life = 5, 730 Years

6. Half Life of Radioactive Atoms
The half-life of an element is the time it takes for half of the material you started with to decay.
2. Each element has it’s own half-life
Each element decays into a new element
4. The half-life of each element is constant. It’s like a clock keeping perfect time.

11. Practice Problems
The half life of iodine-131 is 8.1 days. How long will it take for the sample to reduce to ¼ its original amount?
How long would it take iodine to reduce to less than 1% its original amount?
Radon-222 is a radioactive gas. How long is its half-life if it takes 65 days to reduce to 1/16th its original amount?
Uranium-238 decays very slowly, with a half-life of 4.47 billion years. What percentage of a sample of U-238 would remain after 13.4 billion years?

12. Practice Problems
The half life of iodine-131 is 8.1 days. How long will it take for the sample to reduce to ¼ its original amount?
1  ½  ¼ 2 half lives
2 x 8.1 = 16.2 days

13. Practice Problems
2. How long would it take iodine to reduce to less than 1% its original amount?
100%  50%  25%  12.5%  6.25%  3.125%  1.56%  0.781%
7 half lives 7 x 8.1 days = 56.7 days

14. Practice Problems
3. Radon-222 is a radioactive gas. How long is its half-life if it takes 65 days to reduce to 1/16th its original amount?
1  ½  ¼  1/8  1/16
4 half lives 65 days/4 = days

15. Practice Problems
4. Uranium-238 decays very slowly, with a half-life of 4.47 billion years. What percentage of a sample of U-238 would remain after 13.4 billion years?
13.4 / 4.47 = 3 half lives
100%  50%  25%  12.5%