if uranium-238 undergoes alpha decay the daughter nucleus will be
Alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons. It has a charge of 6981320435297400000♠+2 e and a mass of 7000400000000000000♠4 u. For example, uranium-238 decays to form thorium-234. Alpha particles have a charge 6981320435297400000♠+2 e, but as a nuclear equation describes a nuclear reaction without considering the electrons – a convention that does not imply that the nuclei necessarily occur in neutral atoms – the charge is not usually shown.