---
title: "The potential energy curves for two homonuclear diatomic halogen molecules, \\(\\text{Cl}_2\\text{(g)}\\) and \\(\\text{Br}_2\\text{(g)}\\), are shown in the graph below.  Which curve represents \\(\\text{Br}_2\\text{(g)}\\), and which statement provides the correct justification?"
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url: "https://nerd-notes.com/ubq/121499/"
date_modified: "2026-08-23T05:04:50+00:00"
---

# The potential energy curves for two homonuclear diatomic halogen molecules, \(\text{Cl}_2\text{(g)}\) and \(\text{Br}_2\text{(g)}\), are shown in the graph below.

Which curve represents \(\text{Br}_2\text{(g)}\), and which statement provides the correct justification?

The potential energy curves for two homonuclear diatomic halogen molecules, \(\text{Cl}_2\text{(g)}\) and \(\text{Br}_2\text{(g)}\), are shown in the graph below.

Which curve represents \(\text{Br}_2\text{(g)}\), and which statement provides the correct justification?

![A two-dimensional line graph displays potential energy on the vertical y-axis versus internuclear distance on the horizontal x-axis. A horizontal dotted reference line marks zero potential energy. No numerical gridlines are shown. Two distinct curves are plotted: Curve 1 is drawn as a solid black line, and Curve 2 is drawn as a dashed black line. Curve 1 descends steeply from high positive potential energy at small internuclear distances to a deep minimum located at a relatively short internuclear distance, then rises smoothly to approach the zero energy line asymptotically. Curve 2 begins at a slightly larger internuclear distance, descends to a shallower minimum located further to the right (at a greater internuclear distance and less negative potential energy than Curve 1), and then rises asymptotically toward zero. A legend in the upper-right corner indicates that the solid line represents Curve 1 and the dashed line represents Curve 2. No other lines, labels, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787461490-EjpvHz.jpg)

- **A.** Curve 1, because \(\text{Br}\) has a larger effective nuclear charge than \(\text{Cl}\), which draws the nuclei closer together and increases the covalent bond energy.
- **B.** Curve 2, because \(\text{Br}\) has a larger atomic radius than \(\text{Cl}\), resulting in a greater equilibrium bond distance and a lower bond dissociation energy.
- **C.** Curve 1, because \(\text{Br}_2\) has stronger London dispersion forces than \(\text{Cl}_2\), leading to a deeper potential energy well and a shorter equilibrium bond distance.
- **D.** Curve 2, because \(\text{Br}_2\) has a greater bond order than \(\text{Cl}_2\), which increases the equilibrium bond distance between the two bonded atoms.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121499/*