In a nuclear reaction, the quantities that remain the same before and after the reaction are:
- The total number of protons (which can include protons emitted, transformed into neutrons, etc., keeping the sum the same across the reaction).
- The total number of nucleons (total of protons and neutrons) must also stay the same.
However, in terms of the choices you've provided, the correct response would be the total number of protons.
The energy and types of atoms may change during the nuclear reaction, as new atoms can be formed, and energy can be released or absorbed. The number of alpha particles can also change depending on the specifics of the reaction.