His great discovery, Schrödinger's wave equation, was made at the end of this era - during the first half of 1926. He saw electrons as continuous clouds that crossed over each other. Schrödinger combined some particle behavior with wave behavior and formulated the first mathematical model for the hydrogen atom. He said that the electrons were some where in the 3-dimennisonal space at any given time, but he could not say exactly where they were. Schrödinger also said that the energy levels could have different shapes.