5 April 1913

On this day, 5 April 1913, Niels Bohr completed his groundbreaking paper concerning quantum theory of the hydrogen atom, 'On the constitution of atoms and molecules'. The discoveries of the electron and radioactivity at the end of the 19th century led to different models for the structure of the atom. In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well-defined quantities. Electrons should move around the nucleus but only in prescribed orbits. When jumping from one orbit to another with lower energy, a light quantum is emitted. Bohr's theory could explain why atoms emitted light in fixed wavelengths. - Nobel Prize