Normally, I prefer to do my own research, but I'm drawing a blank on this one. Any help would be appreciated. My understanding is that statistical mechanics accounts for all of the heat energy in a gas by the kinetic energy of the molecules. I also understand that atomic orbitals have different energy levels, and because of the links between heat, radiation, and orbitals, I assume that the atomic orbitals must contribute to the heat energy of a gas. But this seems to be a contradiction with statistical mechanics where all of the heat energy is in kinetic energy.