In chemistry, bond energy (E) is the measure of bond strength in a chemical bond. It is the heat required to break one mole of molecules into their individual atoms. For example, the carbon-hydrogen bond energy in methane E(C–H) is the enthalpy change involved with breaking up one molecule of methane into a carbon atom and 4 hydrogen radicals divided by 4.
Bond energy (E) should not be confused with bond-dissociation energy. It is a roughly transferable property, and enthalpy of formation can typically be roughly approximated by simply adding tabulated values for bond energies for all bonds in a molecule, with an error of sometimes just a few percent. However, to get a better approximation is much more difficult.