Question

which of the following graphs shows potential energy versus bond length for an i₂ molecule?

Explanation:

Step1: Recall bond - energy relationship

The potential energy of a di - atomic molecule like \(I_2\) has a minimum at the equilibrium bond length. As the bond length decreases from the equilibrium value, the potential energy increases sharply due to electron - electron and nucleus - nucleus repulsions. As the bond length increases from the equilibrium value, the potential energy also increases as the bond is stretched and eventually broken.

Step2: Consider \(I_2\) bond length

The equilibrium bond length of \(I_2\) is around 266 pm.

Step3: Analyze the graphs

All the graphs show the general shape of a potential - energy vs bond - length curve (a U - shaped curve). But we need to consider the position of the minimum. Since the equilibrium bond length of \(I_2\) is around 266 pm, the graph that has the minimum of the potential - energy curve at approximately 266 pm is the correct one. Looking at the graphs, graph B has the minimum of the curve closest to 266 pm.

Answer:

B.