How much of a radioactive parent isotope will remain after 3 half-lives have passed?
A)one-third
B)three-halves
C)one-eighth
D)one-sixth

Question

Quizplus · Accepted Answer

After one half-life, half of the parent isotope will remain.
After two half-lives, (1/2) x (1/2) = 1/4 of the parent isotope will remain.
After three half-lives, (1/2) x (1/2) x (1/2) = 1/8 of the parent isotope will remain. Therefore, the answer is C, one-eighth.

How Much of a Radioactive Parent Isotope Will Remain After