Answer:
![a=64.7mg](https://img.qammunity.org/2021/formulas/chemistry/high-school/rzkzi11qaeqf95vx1dfgnt5c3hawb82uit.png)
Step-by-step explanation:
Hello,
In this case, we need to remember that for the required time for a radioactive nuclide as radium-226 to decrease to one half its initial amount we are talking about its half-life. Furthermore, the amount of remaining radioactive material as a function of the half-lives is computed as follows:
![a=a_0((1)/(2) )^{(t)/(t_(1/2)) }](https://img.qammunity.org/2021/formulas/chemistry/high-school/xt8nxfso34yorni77iwr1i5nx4jvipsz3k.png)
Therefore, for an initial amount of 100 mg with a half-life of 1590 years, after 1000 years, we have:
![a=100mg((1)/(2) )^{(1000years)/(1590years) }\\\\a=64.7mg](https://img.qammunity.org/2021/formulas/chemistry/high-school/nv994goeypg16se18cmaense3qittaoudb.png)
Best regards.