1. A is for Atom
A is for Atom

3. 25.2 Half-Life of Radioisotopes
Half-Life t1/2 is the time it takes for half ½ of the amount of a radioisotope to decay and become a new element

4. Example fossil dating
The t1/2 for C-14 is 5700 years At t=0 years a fossil has is 3 g of C-14 At t=5700 years there is now ____ g At t = 11,400 years there is now ____ g At t = ______ years there is now _____ g

5. Half-Life Curve

6. Concentration of old and new elements

7. Half-lives of famous isotopes…
Sodium hours
Iodine days
Hydrogen years
Carbon years
Uranium billion years

8. Practice Write the beta decay for Sodium-24.
What new isotope is formed?
How much new isotope is formed after 45 hours?
How much old isotope is left after 45 hours?

9. Journal
How much old isotope is present after 5 half lives in % and in fraction
How much new isotope is present?
Which isotopes from your list would you choose for fossils that are
500 years
5000 years
1 billion years