The half-life of a radioactive isotope is . If the initial mass of the isotope was , the mass of it — Nuclear Chemistry and Radioactivity Chemistry Question

💡 Solution & Explanation

The number of half-lives elapsed is $n = \frac{t}{T_{1/2}} = \frac{18}{3} = 6$. The amount remaining after $n$ half-lives is given by $N_t = N_0 (1/2)^n$. Therefore, the mass remaining is $256 \times (1/2)^6 = 256 / 64 = 4.0\text{ g}$.