Question

Complete these sentences by selecting the correct answers from the drop-down menus.

After one half-life,
% of the atoms will change to a stable isotope and
% will remain radioactive.

After three half-lives,
% of the atoms will change to a stable isotope and
% will remain radioactive.

Answer 1

After one half-life,

50% of the atoms will change to a stable isotope and

50% will remain radioactive.

After three half-lives,

87.5% of the atoms will change to a stable isotope and

12.5% will remain radioactive.

Explanation:

During the 1st half-life, 50% of the atoms change to a stable isotope, 50% radioactive left.

During the 2nd half-life, 50% of the left 50% radioactive change to a stable isotope, which is 25% of the total. 50% of 50% radioactive left, which is 25% of the total. Then 75% change to a stable isotope and

25% remain radioactive.

During the 3rd half-life, 50% of the left 25% radioactive change to a stable isotope, which is 12.5% of the total. 50% of 25% radioactive left, which is 12.5% of the total. Then 87.5% change to a stable isotope and

12.5% remain radioactive.