Bond energy

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Bond energy

KEY TERMS

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 attractionRange of bond energies, kJ/mol
Ionic bonds7004000
Covalent triple bonds8001000
Covalent double bonds500700
Covalent single bonds200500
Dipole attractions between molecules40400
Hydrogen bonds1040
Table 2. Average Bond Energies of Common Bonds. (Thomson Gale. )
Average bond energies of common bonds
BondBond energies, kJ/mol
CC347
C=C615
CC812
CO360
C=O728
FF158
CLCL244
CH414
HH436
HO464
O=O498

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

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