Question

Write a hypothesis about how the number of half-lives affects the number of radioactive atoms. Use the "if . . . then . . . because . . ." format and be sure to answer the lesson question: "How does the number of radioactive atoms change over time?"

Answer 1

If the number of half-lives that pass increases, then the number of radioactive atoms will decrease by half for each half-life (after n half-lives only (1/2)^n of the original atoms remain), because radioactive decay causes a constant fraction of the remaining unstable atoms to decay in each half-life.

How does the number of radioactive atoms change over time? It decreases exponentially over time, halving every half-life and approaching zero asymptotically.