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 Lowest possible temperature, according to the kinetic theory of gases, attained when a system is at its minimum possible energy, equal to 0 K (-273.15° C and -459.67 F). Temperature is a reflection of molecular energy, thus there must be a point at which no further energy can be extracted. 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 Any energy state of an atom, or of a solid, above its ground state. For atoms and solids, excited states refers to energy levels of electrons higher than the ground-state energy. Excited states are not indefinitely stable, so the atom will eventually return to its ground 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.