TeXes Science Practice Test

When the bond energy of a molecule decreases, what typically happens to its polarity?

1. It increases

2. It decreases

3. It remains unchanged

4. It becomes more stable

The correct answer is: It decreases

The decrease in bond energy of a molecule typically indicates that the bonds holding the atoms together are weaker. Weaker bonds can result from changes in the types of atoms or the nature of the bonds themselves, such as a shift from ionic to covalent bonding or changes in electronegativity differences between the involved atoms. When bond energy decreases, it usually suggests that the molecular structure is less stable, which can lead to a rearrangement of electron distribution. The change in bond strength can alter how electrons are shared between atoms. If the sharing of electrons becomes more unequal due to changes in bonding or atom types, this could lead to an increase in polarity. However, the question focuses specifically on the bond energy's impact. In this context, the correlation between a decrease in bond energy and the decrease in polarity becomes clearer. Weaker bonds may imply that the atoms are less likely to hold onto their electrons tightly, resulting in less significant differences in charge distribution. This erosion of charge separation contributes to a lower overall polarity of the molecule. Thus, the decrease in bond energy is associated with reduced polarity.