Applied Physics and Mathematics Annotation << Back PHOTON SPIN AND ITS ENERGY V.D. PAVLOV When a hydrogen-like atom passes from one stationary state to another, the orbital angular momentum changes. The difference is attributed to a photon and is called the photon’s spin. The theorem is proved: The spin of a photon is equal to zero. The defect in the angular momentum of an atom during radiation can be easily attributed to the nucleus of an atom and even to an electron. In the latter case, the reorientation of the electron spin is just equal to Keywords: hydrogen-like atom, stationary state, orbital angular momentum, photon, spin, angular momentum defect, electron. DOI: 10.25791/pfim.06.2021.1215 Pp. 26-27.