A common example of alpha decay is 
 ${}_{92}{}^{238}\mathrm{U}\to {}_{90}{}^{234}\mathrm{Th}+{}_2{\mathrm{He}}^4+\mathrm{Q}$
Given: 
$$\begin{gathered} {}_{92}{}^{238}\mathrm{U}\mathrm{\hspace{0.17em}}=238.05060\mathrm{u}, \\ {}_{90}{}^{234}\mathrm{Th}\hspace{0.17em}=234.04360\mathrm{\hspace{0.17em}}\mathrm{u}, \\ {}_{90}{}^{234}\mathrm{He}\hspace{0.17em}=4.00260\mathrm{\hspace{0.17em}}\mathrm{u},\hspace{0.17em}\mathrm{and} \\ 1\hspace{0.17em}\mathrm{u}\hspace{0.17em}=931.5\mathrm{\hspace{0.17em}}\frac{\mathrm{MeV}}{{\mathrm{c}}^2} \end{gathered}$$
 The energy released (Q) during the alpha decay of ${}_{92}{}^{238}\mathrm{U}$ is __ MeV