Scientific study of the structure of the atom , its energy states, and its interaction with other particles and fields.
The modern understanding of the atom is that it consists of a heavy nucleus of positive charge surrounded by a cloud of light, negatively charged electrons . The physical properties of atoms are largely determined by the laws of quantum mechanics and quantum electrodynamics . The primary tools for the study of these properties are spectroscopy , particle collisions (see particle accelerator ), and statistical models that simulate complex, many-body interactions (such as gas dynamics). A broad field, atomic physics has applications in the study of condensed matter, gases, chemical-reaction mechanisms, atmospheric science, lasers, nuclear physics , and the arrangement of elements in the periodic table.