

I'm Late, I'm Late, for a Radioactive Date!
Student Sheet #3


Name: ______________________________________
Amount of Pu in grams 
# of halflives (time periods) 
Time in Years 
Fraction of Pu left 
Percent of Pu left 
100 g 
0 
0 (start) 
1 
100% 

1 
5 years 
1/2 
50% 

2 
10 years 
1/4 


3 
15 years 



4 




5 




6 



What is the general formula for determining halflife? _________________
Interactive Site: http://vcourseware.sonoma.edu/VirtualDating/files/RC0/RC_0.html
Answer the following:
1. Generated in the upper atmosphere, C14 makes up only ____% of all carbon atoms.
2. Because of interaction and exchange with atmosphere and oceans, all living tissue maintains a _______ proportion of C14. After death, the amount of C14 begins to ______________.
3. A C14 date estimates the time since the death of onceliving things, up to about _________years.
4. What percent of original C14 can be found in a sample after 10 HL? ____
5. Why is the daughter product, N14, not retained by a specimen? _______
__________________________________________________________
6. Use the decay calculator to determine the age of a rock that has 87% of its mass. __________BP.
7. Use the calculations for the above in BP, substitute it into the calculator,
and determine the date in A.D. _________A.D.
8. Explain why the amount of C14 produced in the Earth's upper atmosphere from cosmic rays striking N14 is or is not constant over time.
__________________________________________________________
__________________________________________________________
__________________________________________________________
__________________________________________________________
9. What would be the age if you used the calibration or correction curves for the time in question 6?
_______________A.D.


