1. Half Life
- A half life is the amount of time that it takes for half of a given sample to decay into something else
Example: Barium-122 has a half-life of 2 minutes. A fresh sample weighing 80 g was obtained.
After 10 minutes, how much will be left?

2. Half Life -Half lives can be used to date different materials
-By knowing the ratio of the isotopes you have, you can determine the age of your sample

3. Half Life -Carbon-14 has a half life on 5730 years
-A sample that contains 100 g of C-14 when it should normally have 200 g is 5730 years old
- A sample that contains 50 g of C-14 when it should normally have 200 g is years old

4. Half Life Practice
1. Iodine-131 is used to destroy thyroid tissue in the treatment of an overactive thyroid. The half-life of iodine-131 is 8 days. If a hospital receives a shipment of 200 g of iodine-131, how much I-131 would remain after 32 days?
2. Technetium-99 is used for brain scans. If a laboratory receives a shipment of 200 g of this isotope and after 24 hours only 12.5 g of this isotope remain, what is the half-life of technetium-99?