(a) Deduce the expression, $\mathit{N}={\mathit{N}}_0{\mathit{e}}^{-\mathit{\lambda }\mathit{t}}$, for the law of radioactive decay.
(b) (i) Write symbolically the process expressing the $\mathit{\beta }+$ decay of ${}_{11}^{22}\mathrm{Na}$. Also write the basic nuclear process underlying this decay.
(ii) If the nucleus formed in the decay of the nucleus ${}_{11}^{22}\mathrm{Na}$, and isotope or isobar?