The negative potential energy means that the object in the well is confined to that region, i.e. it is bound. It has a steep negative slope and a shallower positive slope. The minimum of the well is at the equilibrium separation distance for the atoms and the depth of the well i.e. the minimum potential energy gives the bond energy. An interatomic potential function is given by Joules. The bottom of the potential well is the zero of the force function.
Positive forces are forces in the positive direction i.e. repulsive forces.
Negative forces are forces in the negative direction i.e. attractive forces. The distance to the minimum of the force function is the critical distance to break the bond. The maximum negative force is the critical force to break the bond. The critical distance is always greater than the equilibrium distance. The inert gases have a stable outer level with 8 electrons.