This is analogous to de-excitation of an atomic electron. Gamma decay it only occurs when other decay occurs (alpha/beta). As nuclear states have higher energies in the order of MeV.therefore, the photons emitted by nuclei have very large energies (≈ MeV) and much smaller wavelength (< 0.01 Å). Gamma Decay. GCSE Physics Atomic structure Atomic structure Lesson Progress 0% Complete The nuclear model was devised by Rutherford. AAMC MCAT Biology Section Bank. Gamma rays are emitted by unstable nuclei in their transition from a high energy state to a lower state known as gamma decay. 159 terms. The atomic number and mass number remain the same, but the resulting nucleus assumes a more stable energy state. The atomic number of the daughter nucleus is greater than the atomic number of the parent nucleus by {eq}1 {/eq}. Energy is emitted in all three types of decay, but only alpha and beta decay also emit particles. Nuclear reaction energy, such as released in α decay, can be found using the equation E = (Δm)c 2.We must first find Δm, the difference in mass between the parent nucleus and the products of the decay.This is easily done using masses given in Appendix A. Question: Radioactive Decay Occurs When An Unstable Atomic Nucleus Becomes More Stable By Emitting Radiation And Losing Energy. Atoms with unstable nuclei are radioactive. Gamma Emission. since gamma has no charge, there's no change in the atomic number/mass number. An example is the decay of carbon­14: The final nucleus still has 14 nucleons, but it has one more proton and one fewer neutron. During alpha-decay , a nucleus decays by emitting an -particle ( a helium nucleus ) according to the equation