11.1.6—Nucleon number and charge are conserved in nuclear processes

In a nuclear equation, total nucleon number A and total proton number Z are conserved across the reaction or decay.

Balance A and Z separately; emitted particles carry their own nucleon and charge numbers.

In alpha decay, A falls by 4 and Z by 2 because the emitted alpha particle is ^4_2He.

Conservation of nucleon number does not mean the same nucleus remains; identity and energy can change while totals balance.