1. Half Life

2. Review Pennium Lab:
What (on average) happened to the number of atoms left after 1 half life?
Write your own definition of what a half life is.

3. Half Life
Half Life: the time it takes for half a sample of unstable radioisotopes to decay

4. Elements and their Half Life:
Elements take very different amounts of time to decay to half of the original sample
Some elements can take seconds, some can take billions of years

5. Applications?
Radioactive dating: Carbon-14 is used to determine the age of ancient things.
Medical diagnostic tests (i.e. bone density scan)

6. Example Problem
The half-life of Po-218 is three minutes. How much of a 2.0 gram sample remains after 15 minutes?

7. Practice
How many half-lives have passed for each of the following samples:
a. 50% of the original radioactive material remains ____________
b. 25% of the original radioactive sample remains ____________
c % of the original radioactive sample remains ____________

8. Practice
Carbon-14 is a radioactive element that decays into Nitrogen-14. The half-life of Carbon-14 is 5730 years. What percentage of Carbon-14 and Nitrogen-14 will be left in a dinosaur bone after:
5730 years: % of Carbon-14 _________
11,580 years: % of Carbon-14 _________
17,310 years: % of Carbon-14 _________