Nuclear physics is the field of physics that studies the constituents and interactions of
atomic nuclei. The most commonly known applications of nuclear physics are nuclear power
generation but the research has provided application in many fields including those in
nuclear medicine and magnetic resonance imaging nuclear weapons ion implantation in materials
engineering and radiocarbon in geology and archaeology. The field of particle physics evolved
out of nuclear physics and is typically taught in close association with nuclear physics. A
heavy nucleus can contain hundreds of nucleons which means that with some approximation it can
be treated as a classical system rather than a quantum-mechanical one. In the resulting
liquid-drop model the nucleus has an energy which arises partly from surface tension and
partly from electrical repulsion of the protons. The liquid-drop model is able to reproduce
many features of nuclei including the general trend of binding energy with respect to mass
number as well as the phenomenon of nuclear fission. Superimposed on this classical picture
however are quantummechanical effects which can be described using the nuclear shell model
developed in large part by Maria Goeppert-Mayer and J. Hans D. Jensen. Nuclei with certain
numbers of neutrons and protons (the magic numbers 2 8 20 28 50 82 126 ...) are
particularly stable because their shells are filled. Other more complicated models for the
nucleus have also been proposed such as the interacting boson model in which pairs of
neutrons and protons interact as bosons analogously to Cooper pairs of electrons.
