Arnold Johannes Wilhelm Sommerfeld.

German physicist who did important work on the atom, providing the new theory on the elliptical orbits.

Born in Königsberg on December 5, 1868, and there made his university studies, as a student of Hilbert and Lindermann. He was Professor of theoretical physics at the technical school of Aachen, at the University of Berlin and later at the University of Munich, city in which he lived much of his life. Died in Munich on April 26, 1951.Entre his works stand out "Atoms and spectral lines" (1919) and "Introduction to theoretical physics" (1948).It carries out various studies concerning the formulation of the theory of the gyroscope, the propagation of radio waves, the wave-like nature of x-rays, but mainly include those related to rays of the spectrums applying advances in relativistic theory and quantum mechanics; It also establishes the relationship between electric and heat capacity of metals and deduces the quantum theory of electrons in metals (1928).

In 1915, modifies the Danish physicist Niels Bohr atomic theory based on quantum and Relativistic, theories because it failed to try to explain complex atoms; It means also that orbits that describe electrons are elliptic and are defined by a second quantum number l called azimuth, or secondary quantum number which takes values between 0 and n-1, where n is a positive whole number which corresponds to the principal quantum number, obtained by Bohr. This quantum number determines eI angular momentum of the electron and if this particle has angular momentum will turn angular kinetic energy that will be delimited by the total energy of the electron. It also introduced a third quantum number, the magnetic quantum number m, which indicates the inclination of the plane of the orbit in space and can take values ranging between - l and + l.En 1916, F. Paschen found the hypothesis of Sommerfeld.Este Atomic model of Bohr-Sommerfeld together with the exclusion principle enunciated by the physicist Wolfgang Pauli in 1824, according to which there could be two electrons in a same orbit with the same quantum numbers, and the introduction of a fourth quantum number, when also in 1824 Goudsmit and Unlenbeck formulated the hypothesis that electrons revolve with rotating around its axis motion and have therefore a mechanical angular momentum (spin) and a magnetic moment, allowed to give a clear interpretation of the periodic system of the elements and the same chemical behavior; However this theory was never considered as final as it raised an issue with the discontinuity of energy, and required the base which then provided the quantum Wave mechanics, which finally allowed a better interpretation of the Spectra to the Bohr-Sommerfeld model. Subsequently this model was replaced in one based on wave mechanics, where the Austrian physicist Erwin Schrödinger wave function describes the conduct of any atomic system, and thus the quantum numbers are an automatic consequence of this equation.