Ground State

Energy state of an atom, or of a solid, when its total energy equals the minimum possible energy for that atom or solid. For solids, this only occurs at a temperature of absolute zero. Individual atoms may be in their ground state at non-zero temperatures, but they will not stay there indefinitely. Instead, they can occasionally absorb thermal energy and move to an excited state for a while before they decay back to the ground state. For the energy levels of electrons in atoms and solids, the “ground state” refers to the situation when all electrons have their lowest possible energies.

Some or all content above used with permission from J. H. Wittke.