Answer to Question #157000 in Atomic and Nuclear Physics for Fouad Righi

Question

A 145 gram sample of a certain radioactive isotopes had a half-life of 500 years. If 4 half-lives go by, how much of the original isotope is left?

Answer 1

One half-life: $\frac{145}{2}=72.5 \;g$

Two half-lives: $\frac{72.5}{2}=36.25 \;g$

Three half-lives: $\frac{36.25}{2}=18.125 \;g$

Four half-lives: $\frac{18.125}{2}=9.0625 \;g$

Answer: 9.0625 g