a) \displaystyle \mathrm{^{230}_{90}Th\, \longrightarrow \,^{226}_{88}Ra +\, ^4_2 He}
b) \displaystyle \mathrm{Q = (230,033128 -\, 226,025402 -\, 4,002603)uc^2 = 5,123\, 10^{-3}\, uc^2 = 4,772\, MeV}
