NAME __________________KEY________________________________DATE _________________
Half-life Practice
1. What is half-life? ___________The time it takes for 1/2 or a radioactive isotope to decay. ______
2. If we start with 400 atoms of a radioactive substance, how many would we have after:
a. one half-life? ___200______ c. three half-lives? __50_______
b. two half-lives? ___100______ d. four half-lives? __25_______
3. If we start with 48 atoms of a radioactive substance, how many would remain after:
a. one half-life? ___24______ c. after three half-lives? _____6_____
b. two half-lives? ___12_____ d. after four half-lives? _____3_____
Using the graph to the right, answer
the following questions.
4.What is the half-life of each element?
A = 0.75 x 109 years (7.5 x 108 years)
B = 4.5 x 109 years
C = 13 x 109 years (1.3 x 1010 years)
D = Unknown
5.Which element has the shortest half-life?
A
6.Which element is the most unstable? How
do you know? A because it has the shortest half life.
Use the graph on the to answer the following questions.
7. How many atoms are in the original sample size of this
radioisotope? 80 atoms
8. How long is the half-life? 2 days
9. How many atoms are left after 2 half-lives? 20 atoms
10. Approximately how many days would have to pass for
there to be only 2.5 atoms of the sample remaining? How
many half-lives? 10 days (5 half lives)
Half-life Practice
1. What is half-life? ___________The time it takes for 1/2 or a radioactive isotope to decay. ______
2. If we start with 400 atoms of a radioactive substance, how many would we have after:
a. one half-life? ___200______ c. three half-lives? __50_______
b. two half-lives? ___100______ d. four half-lives? __25_______
3. If we start with 48 atoms of a radioactive substance, how many would remain after:
a. one half-life? ___24______ c. after three half-lives? _____6_____
b. two half-lives? ___12_____ d. after four half-lives? _____3_____
Using the graph to the right, answer
the following questions.
4.What is the half-life of each element?
A = 0.75 x 109 years (7.5 x 108 years)
B = 4.5 x 109 years
C = 13 x 109 years (1.3 x 1010 years)
D = Unknown
5.Which element has the shortest half-life?
A
6.Which element is the most unstable? How
do you know? A because it has the shortest half life.
Use the graph on the to answer the following questions.
7. How many atoms are in the original sample size of this
radioisotope? 80 atoms
8. How long is the half-life? 2 days
9. How many atoms are left after 2 half-lives? 20 atoms
10. Approximately how many days would have to pass for
there to be only 2.5 atoms of the sample remaining? How
many half-lives? 10 days (5 half lives)
