Concept: The stability of a molecule is inversely proportional to its potential energy. A lower potential energy corresponds to a more stable state. In a potential energy curve for bond formation, the minimum point represents the most stable state where the attractive and repulsive forces between the atoms are balanced, and the bond length is optimal.

Why (B) is correct: The potential energy curve shows the energy of the system as a function of the internuclear distance between two hydrogen atoms. The lowest point on this curve represents the most stable state of the molecule. At this point, the attractive forces between the nuclei and electrons are maximized, and the repulsive forces between the nuclei and between the electrons are minimized, leading to the formation of a stable chemical bond. Point C is the minimum point on the potential energy curve, indicating the lowest potential energy and thus the most stable state for the ${\mathrm{H}}_2$ molecule.

Option Analysis:

• A) A: At point A, the internuclear distance is very large, meaning the hydrogen atoms are far apart and essentially non-interacting. The potential energy is close to zero, indicating no bond formation and thus not a stable molecular state.
• B) C: At point C, the potential energy is at its minimum. This corresponds to the equilibrium bond length where the attractive and repulsive forces are balanced, and the ${\mathrm{H}}_2$ molecule is in its most stable state.
• C) B: Point B is at a larger internuclear distance than C, meaning the atoms are still approaching each other, and the potential energy is decreasing but has not yet reached its minimum. It is a less stable state than C.
• D) D: At point D, the internuclear distance is very small. The nuclei are too close, leading to strong internuclear repulsion. This results in a very high positive potential energy, indicating an unstable state where the atoms repel each other strongly.

Correct Answer: (B)