The half-life of Au^198 is 2.7 days. The activity of 1.50 mg of Au^198 if its atomic weight is 198 g mol^-1 is, ( N_A =6 × 10^23 / mol ).

The half-life of $\displaystyle \mathrm{Au}^{198}$ is $\displaystyle 2.7$ days. The activity of $\displaystyle 1.50$ mg of $\displaystyle \mathrm{Au}^{198}$ if its atomic weight is $\displaystyle 198 \mathrm{~g} \mathrm{~mol}^{-1}$ is, $\displaystyle \left(\mathrm{N}_{\mathrm{A}}=6 \times 10^{23} / \mathrm{mol}\right)$.