TeXes Science Practice Test

What effect does a decrease in electronegativities of bonded atoms have on the bond energy of heterodiatomic molecules?

1. It increases

2. It remains the same

3. It decreases

4. It becomes unstable

The correct answer is: It decreases

A decrease in electronegativities of bonded atoms typically leads to a decrease in bond energy in heterodiatomic molecules. When the electronegativities of the two bonded atoms are closer together, the difference in electron affinity is reduced, resulting in a less polar bond. This means the atoms do not hold onto the shared electrons as strongly, leading to weaker bonds. Weaker bonds correlate to lower bond energy because less energy is required to break these bonds. In contrast, when there is a significant difference in electronegativities, the resulting polar bond exhibits stronger interactions due to partial charges, which increases bond energy. Thus, as the electronegativities converge and become less different, the strength of the bond diminishes, further emphasizing the relationship between electronegativity, bond type, and bond energy.