  Within the Sommerfeld atomic model the quantization of magnetic flux through
the electronic orbits is investigated together with its dependency on
additional sources of magnetic fields. These sources alter the magnetic flux
through the atomic orbits and in consequence are causing energy shifts. This
effect is investigated for the cases, where the source is an external magnetic
field, the magnetic moment of the nucleus or the magnetic moment of the
electron. The energy shifts due to external magnetic fields, the magnetic
dipole contribution of the hyperfine splitting and the spin-orbit coupling can
be reproduced very well. The meaning of 'spin', however, changes within this
approach drastically. The unusual Land\'e g-factor of 2 for the electron is a
result of the orbital motion and the magnetic moment of the electron rather
than it is an intrinsic property of the electron.
