The expectation value of the total energy of a wave packet, associated with the speed (moments) space by means of the Lorentz transformation, allows us to obtain by means of quantum wave formulation an energetic expression equivalent, and at the same time less restricted (more versatile and informative), to the one obtained by means of a corpuscular treatment. On the one hand, the energetic formants of the matter appear, on the other the expression in undulatory terms of it, of that which we call mass, and finally an additional phase factor as the last vestige of the undulatory nature after the formation process, that is to say, as an accrediting element of that nature, and mechanism of restitution of it, responsible for the wave-corpuscle duality, of the related creation-annihilation processes, and of the relations among the different generations of elementary particles, as it was shown in https://vixra.org/abs/2003.0001.