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

To complete the sentences regarding the decay of radioactive isotopes:

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.

(Note: After three half-lives, 1/2 of the remaining 50% will be radioactive, followed by 1/2 of that remaining amount in the next cycle, resulting in a cumulative change to a stable isotope.)