When`plpha`-particle is emitted by an atom, its atomic number decreases by 2 and mass number decreases by 4. Also, when `beta`-particle is radiated the atomic number increases by 1 and mass number does not change. Thus when `_(90)Th^(232)` is disintegrated into `_(82)Pb^(200),8alpha` particles and `8beta` particles are emiited.
