ground state

The ground state is the condition of an atom, ion, or molecule, when all of its electrons are in their lowest possible energy levels, i.e., not excited. When an atom is in its ground state, its electrons fill the lowest energy orbitals completely before they begin to occupy higher energy orbitals, and they fill subshells in accordance with Hund's rule (usually!)


In the case of an atomic nucleus, the ground state is the lowest, most stable energy state of a nucleus.