Post your articles online and promote your website for free! Boost your sites ranking by linking it from the ArticleZap database! Free Article directory and instant translation publishing!
collective model, description of atomic nuclei that incorporates aspects of both the shell model and the liquid-drop model to explain certain magnetic and electric properties that neither of the two separately can explain. Whereas in the shell model nuclear structure and behaviour are explained on the basis of unpaired nucleons (protons and neutrons) beyond the passive nuclear core composed of closed shells of paired protons and paired neutrons, and whereas in the liquid-drop model nuclear structure and behaviour are explained on the basis of all the nucleons contributing statistically (much as the molecules of a spherical drop of water contribute to the overall energy and surface tension), in the collective model high-energy states of the nucleus and certain magnetic and electric properties (magnetic and quadrupole moments) can be explained by the joint motion of the unpaired nucleons outside the closed shells and the combined motion of the paired nucleons in the core.
Roughly, the nuclear core may be thought of as a liquid drop on whose surface circulates a stable tidal bulge directed toward the rotating unpaired nueleons outside the bulge. The tide of protons (positively charged particles) constitutes a current that in turn contributes to the magnetic properties of the nucleus, and the greater deformation of the nucleus as the number of unpaired nucleons increase accounts nicely for the measured electric quadrupole moment (which may be considered as an index of nuclear shape or a measure of how niuch the distribution of electric charge in space departs from spherical symmetry).
