The given figure shows the potential energy curve for the formation of the ${\mathrm{H}}_2^{+}$ ion. The stability of a molecular system is inversely proportional to its potential energy; a lower potential energy corresponds to a more stable state.

Analysis of the Curves:

• Curve-1: This curve shows a continuous decrease in potential energy as the internuclear distance decreases, but it does not reach a minimum. This indicates a purely repulsive interaction or a state where the atoms are not forming a stable bond.
• Curve-2: This curve shows an initial decrease in potential energy as the internuclear distance decreases, reaching a minimum at a specific internuclear distance (the bond length), and then increasing sharply at very short distances due to internuclear repulsion. The minimum in the potential energy curve represents the most stable state of the molecule, where the attractive and repulsive forces are balanced, and the bond is formed.

Option Analysis:

• A) Curve-1 represents the most stable state of the system for ${\mathrm{H}}_2^{+}$ ion: This is incorrect. Curve-1 does not show a minimum, indicating no stable bond formation.
• B) Curve-2 represents the most stable state of the system for ${\mathrm{H}}_2^{+}$ ion: This is correct. The minimum in Curve-2 corresponds to the lowest potential energy, which signifies the most stable state of the ${\mathrm{H}}_2^{+}$ ion at its equilibrium bond length.
• C) Curve-1 indicates that the molecular hydrogen ion is formed: This is incorrect. Curve-1 represents a repulsive interaction, not the formation of a stable molecular ion.
• D) Curve-2 represents the energy level of the antibonding region: This is incorrect. Curve-2 represents the potential energy of the bonding molecular orbital, leading to a stable bond. The antibonding region would correspond to a curve that is entirely repulsive or has a higher energy than the separated atoms.

Correct Answer: (B)