Concept: The formation of a chemical bond between two atoms involves a decrease in potential energy, leading to a more stable state. The potential energy diagram for bond formation typically shows potential energy on the y-axis and internuclear distance on the x-axis.

Why (D) is correct:

The graph illustrates the potential energy changes as two hydrogen atoms approach each other to form an H₂ molecule.

• At point 'a', the atoms are far apart, and there is essentially no interaction between them, so the potential energy is close to zero.
• As the atoms approach each other, attractive forces (electron-nucleus interactions) dominate, causing the potential energy to decrease.
• Point 'c' represents the internuclear distance where the attractive and repulsive forces are balanced, and the potential energy is at its minimum. This minimum potential energy corresponds to the most stable state, which is the bond length of the H₂ molecule. Therefore, point 'c' signifies the formation of the chemical bond.
• Beyond point 'c', if the atoms are forced closer (e.g., point 'd'), repulsive forces (nucleus-nucleus and electron-electron interactions) become dominant, causing the potential energy to increase sharply.

Option Analysis:

• A) a: Represents two isolated atoms with no interaction, not bond formation.
• B) d: Represents a state where atoms are too close, and strong repulsive forces exist, leading to high potential energy, not bond formation.
• C) e: Represents a state where atoms are closer than 'a' but not at the optimal bond length, and the potential energy is still decreasing towards the minimum.
• D) c: Represents the minimum potential energy, which is the most stable state and corresponds to the formation of the chemical bond at the equilibrium bond length.

Correct Answer: (D)