Bond energy
Bond energy
Bond energy is the strength of a chemical bond between atoms, expressed as the amount of energy required to break it apart. It is as if the bonded
| Table 1. Typical Bond Energies. (Thomson Gale. ) | |
|---|---|
| Typical bond energies | |
| Type of bond or attraction | Range of bond energies, kJ/mol |
| Ionic bonds | 700–4000 |
| Covalent triple bonds | 800–1000 |
| Covalent double bonds | 500–700 |
| Covalent single bonds | 200–500 |
| Dipole attractions between molecules | 40–400 |
| Hydrogen bonds | 10–40 |
| Table 2. Average Bond Energies of Common Bonds. (Thomson Gale. ) | |
|---|---|
| Average bond energies of common bonds | |
| Bond | Bond energies, kJ/mol |
| C–C | 347 |
| C=C | 615 |
| C≡C | 812 |
| C–O | 360 |
| C=O | 728 |
| F–F | 158 |
| CL–CL | 244 |
| C–H | 414 |
| H–H | 436 |
| H–O | 464 |
| O=O | 498 |
atoms were glued together: the stronger the glue is, the more energy would be needed to break them apart. A higher bond energy, therefore, means a stronger bond.
Bond energies are usually expressed in kilojoules per mole (kJ/mol): the number of kilojoules of energy that it would take to break apart exactly one mole of those bonds. There are several kinds of “glues,” or attractions, by which atoms and molecules can stick together. Depending upon the type of attractive force, the bond energy can vary in strength. For example, an ionic bond, which is a simple interaction between a positively-charged group and a negatively-charged group, is stronger than a type of bond called a covalent bond, which involves the sharing of electron between the atoms participating in the bond. Among covalent bonds, triple bonds, which involve the sharing of three electrons, are stronger than double bonds and double bonds are stronger than single bonds. Hydrogen
KEY TERMS
Kilojoule— An amount of energy equal to a thousand joules. One kilojoule is equivalent to 0.239 kilocalorie. In electrical terms, a kilojoule is the amount of energy used by one kilowatt of power operating for one second.
bonds are weakest of all these bonds. However, in a molecule there can be many individual hydrogen bonds, so their total strength can be considerable. Hydrogen bonds play an important role in determining the properties of important compounds such as proteins and water.
See also Dipole.
Robert L. Wolke