# 1.7: Lab Exercise (Part C)

## Part C – Radiometric Dating

Complete the following chart by calculating the amount of parent isotope remaining for all of the given half-lives, then plot your findings on the graph (Figure 1.13). Make sure you connect the data points on the graph by drawing in the decay curve.

Use the completed chart and graph to answer the questions below. 13. How much of the parent isotope would be remaining after 7 half-lives have passed?

a. 6.25%                         b. 1.56%                         c. 0.78%                         d. 0.39%

14. If a radiometric element has a half-life of 425 years, how old would a rock be that only had 3.125% of the parent isotope remaining?

a. 2125 years                         b. 1700 years                         c. 2550 years                         d. 3400 years

15. Based on your graph above, approximately how much of the parent isotope would be remaining after 3.5 half-lives?

a. 16%                         b. 12%                         c. 4%                         d. 8%

16. Based on your graph above, approximately how many half-lives have passed when only 35% of the parent isotope is remaining?

a. 0.75                         b. 1.5                         c. 2.1                         d. 2.5