Definition of bond energy (mean bond energy)

The average value of the gas-phase bond-dissociation energies (usually at a temperature of 298 K) for all bonds of the same type within the same chemical species. The mean bond energy for methane, for example, is one-fourth the enthalpy of reaction for

CH4(g) C(g) + 4H(g)

Tabulated bond energies are generally values of bond energies averaged over a number of selected typical chemical species containing that type of bond.