The distance at which the energy is minimum is called the equilibrium internuclear distance or the bond length. 1. The energy terms involved are the potential energy that results from the attractions and repulsions among the charged particles and the kinetic energy caused by the motions of the electrons.2. The zero reference point for energy is defined for the atoms at infinite separation.3. At very short distances the energy rises steeply because of the great importance of the internuclear repulsive forces at these distances.