When the nucleus of an unstable atom emits only gamma radiation, the nucleus must:

Explanation

Radioactive decay results when an element changes to another element by changes within the atom's nucleus. These changes leave the nucleus in an excited state. The atom emits a gamma ray as it decays into the ground state. In gamma decay, a nucleus changes from a higher energy state to a lower energy state through the emission of electromagnetic radiation (photons) and thus loses excess energy. The number of protons (and neutrons) in the nucleus does not change in this process, so the parent and daughter atoms are the same chemical element. Options A, C, and D are incorrect. The emission of gamma radiation does not result in a gain or loss of protons or a gain of energy in the nucleus.