Answer:
When radioactive atoms decay, they release energy in the form of ionizing radiation (alpha particles, beta particles and/or gamma rays). The energy is called ionizing radiation because it has enough energy to knock tightly bound electrons from an atom's orbit. This causes the atom to become a charged ion
I believe this would be an exothermic reaction, As time increases, the temperature goes up meaning the heat from the system is going into the surroundings. Which indicates an exothermic reaction.
