Einstein’s energy-momentum relationship, holds when the energy absorbed by a body is all converted to kinetic energy of that body. However, an electron in an atom acquires kinetic energy through emission of photon energy. Therefore, Einstein’s relationship cannot be applied to an bound electron in an atom. The author has already derived an energy-momentum relationship for an electron in a hydrogen atom. This paper incorporates de Broglie’s formula into the above relationship previously derived by the author. Also, if the momentum of an electron in a hydrogen atom is considered using an ellipse, it can be predicted that the electron has two types of momentum and two types of waves. This paper concludes that a moving electron has two types of waves.