the principle of equipartition of energy in classical statistical mechanics states that each molecular degree of freedom receives 1/2 "kt" of energy, a result which was modified when quantum mechanics explained certain anomalies; e.g., in the observed specific heats of crystals (when "h"ν &gt; "kt"). for monatomic helium and other noble gases, the internal energy consists only of the translational kinetic energy of the individual atoms. monatomic particles, of course, do not (sensibly) rotate or vibrate, and are not electronically excited to higher energies except at very high temperatures.