principal quantum number One of the four quantum numbers that characterize the electron configuration of an atom. The principal quantum number determines the size and (in hydrogen atoms) the energy of an orbital. The principal quantum number, n, is used to label electron shells; n may take on integer values from 1 to infinity. Related categories • ATOMIC AND NUCLEAR PHYSICS • PHYSICAL CHEMISTRY Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) |