Final answer:
As two hydrogen atoms get closer, attractive forces dominate initially and decrease the potential energy, leading to system stability. At very short distances, repulsive forces become stronger, increasing the potential energy and reducing stability. There is an optimal internuclear distance where forces balance, known as the bond length.
Step-by-step explanation:
As two hydrogen atoms approach each other and the distance between their nuclei decreases, the interactions between them change. Initially, the attractive forces between the protons in the nuclei and the electrons of the opposite atom increase as their electron clouds begin to overlap, leading to a decrease in the system's potential energy. This process contributes to the stability of the system. However, at a certain point, as the internuclear distance becomes very short, the repulsive forces between the like-charged electrons and the protons begin to dominate. The potential energy will then increase sharply, indicating a less stable, high-energy system. There is an optimal internuclear distance where these attractive and repulsive forces are in balance, and this is known as the bond length, which for a hydrogen molecule (H₂) is approximately 74 pm.