The half-life of one isotope of radium is about years. In a given sample of this isotope,
of the radium atoms will decay in a time most nearly equal to
Select an Answer
years
years
years
years
years
View Correct Answer
During each half-life, an average of of the nuclei present will decay. So after one half-life only about
of the radium nuclei remain. After two half-lives the sample contains
of
, or about
of the original number of radium nuclei. In general, the number of nuclei remaining after
half-lives have elapsed is
.Having
of the radium nuclei decay means having
of them remain, which is
. So the answer is four half-lives, which is
years.