Question
Example Bond Energies of Ionic Compounds
Li-F = 1036 kJ/mol
Li-Br = 807 kJ/mol
Na-F = 923 kJ/mol
Na-Br = 747 kJ/mol
Given the general trend with bond energies, which of the compounds would have the smallest bond energy?
A. Cs-Br
B. K-Br
C. Cs-F
D. K-F
Li-F = 1036 kJ/mol
Li-Br = 807 kJ/mol
Na-F = 923 kJ/mol
Na-Br = 747 kJ/mol
Given the general trend with bond energies, which of the compounds would have the smallest bond energy?
A. Cs-Br
B. K-Br
C. Cs-F
D. K-F
Answers
GPT-4o mini
To determine which compound would have the smallest bond energy among the given options, we can use the general trend in ionic bond energies. Bond energies for ionic compounds typically decrease with increasing ionic size. This is due to the larger radii of the ions resulting in a weaker electrostatic attraction between the ions.
Going from lithium (Li) to sodium (Na) to potassium (K) to cesium (Cs), the cations increase in size. Likewise, fluorine (F) and bromine (Br) are constant in this comparison.
Based on this reasoning:
- **Cs-Br** would have a weaker bond compared to lower alkali metals because cesium is larger than potassium and lithium.
- **K-Br** would also have a relatively weaker bond than Li-Br but stronger than Cs-Br.
- **Cs-F** would have a weaker bond than K-F because the size of Cs is larger than K.
- **K-F** would have a notably higher bond energy compared to K-Br because the attraction between K and F is stronger than between K and Br due to the smaller size of F compared to Br.
Following this trend, we can conclude that compounds containing the largest cation (Cs) and the larger anion (Br) will have the smallest bond energy.
Thus, the answer is:
**A. Cs-Br**.
Going from lithium (Li) to sodium (Na) to potassium (K) to cesium (Cs), the cations increase in size. Likewise, fluorine (F) and bromine (Br) are constant in this comparison.
Based on this reasoning:
- **Cs-Br** would have a weaker bond compared to lower alkali metals because cesium is larger than potassium and lithium.
- **K-Br** would also have a relatively weaker bond than Li-Br but stronger than Cs-Br.
- **Cs-F** would have a weaker bond than K-F because the size of Cs is larger than K.
- **K-F** would have a notably higher bond energy compared to K-Br because the attraction between K and F is stronger than between K and Br due to the smaller size of F compared to Br.
Following this trend, we can conclude that compounds containing the largest cation (Cs) and the larger anion (Br) will have the smallest bond energy.
Thus, the answer is:
**A. Cs-Br**.