Zeeman effect, Paschen-Back effect & Stark effect

   The electron configuration in a multi electron atom is determined by three factors. a) Attraction from the nucleus, b) repulsion between electrons, and c) buoyant force exerted by space matter (see structure of atom). When an atom is situated in a strong- electric field or magnetic field, its electron configuration is shifted from its normal state. That is, because of the influence of the external field, some electrons in the atom (mostly outer electrons) are shifted from their original shells. When such an atom is excited, the atom can emit different spectrum of radiations relative to its original spectrum lines. This effect is a direct indication for the strength of the field. I.e. when a weak field affects only outer electrons, a strong field can influence both the inner and outer electrons alike. Lighter elements can demonstrate the effect in a weaker field comparatively than heavy elements because of the binding force on the electrons in a lighter element is much less than that of heavy elements.