In the potential energy versus inter molecular distance graph, we know that atoms/molecules/particles want to be at optimum distance from each other ie $r_0$ and to the left of this position in the graph, we get the repulsive force and to the right would be the attractive force acting between them.
Note: Inter-molecular distance is denoted by ‘r’.
However, I have the following questions regarding this graph:
Why does graph represent negative Potential energy after a certain inter-molecular distance ?
What does negative potential energy mean in this context since the repulsive energy at r=0 was positive?
What happens at the point when P.E. becomes zero for a certain inter-molecular distance?
If the P.E. at that point has already reached zero, why is there a further need to go into negative potential energy?