(a)[1]
Define the half-life of a radioactive isotope.
(b(i))[1]
State the quantity shown by the magnitude of the gradient of line $X$ in Fig. 9.1.
(b(ii))[3]
State three conclusions about $X$ or $Y$ that can be drawn from Fig. 9.1. These conclusions may be qualitative or quantitative.
(c)[3]
In the sample in (b), the mass of radioactive isotope $X$ at time $t=0$ is $7.3 \times 10^{-4}\,\text{kg}$. Determine the nucleon number of isotope $X$.