A certain element emits one alpha particle, and its products then emit two beta particles in succession. The atomic number of the resulting element is changed by zero.
Work Step by Step
An alpha particle has two protons and two neutrons, and thus, takes away 2 positive charges. The system's charge is lowered by 2. Each beta particle is negatively charged, so the charge of the system that is left behind after 2 of them leave is higher, by +2. This is discussed on page 629.