Bond Energy Definition in Chemistry

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Bond energy (E) is defined as the amount of energy required to break apart a mole of molecules into its component atoms. It is a measure of the strength of a chemical bond. Bond energy is also known as bond enthalpy (H) or simply as bond strength.

Bond Energy Explained

Bond energy is based on an average of bond dissociation values for species in the gas phase, typically at a temperature of 298 Kelvin. It may be found by measuring or calculating the enthalpy change of breaking a molecule into its component atoms and ions and dividing the value by the number of chemical bonds. For example, the enthalpy change of breaking methane (CH4) into a carbon atom and four hydrogen ions, divided by four (the number of C-H) bonds, yields the bond energy.

Bond energy is not the same thing as bond-dissociation energy. Bond energy values are an average of the bond-dissociation energies within a molecule. Breaking subsequent bonds requires a different amount of energy.

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Helmenstine, Anne Marie, Ph.D. "Bond Energy Definition in Chemistry." ThoughtCo, Aug. 28, 2020, Helmenstine, Anne Marie, Ph.D. (2020, August 28). Bond Energy Definition in Chemistry. Retrieved from Helmenstine, Anne Marie, Ph.D. "Bond Energy Definition in Chemistry." ThoughtCo. (accessed March 28, 2023).