Also called bond enthalpy, bond energy is the energy required to break away two chemically bonded atoms. This energy is definite in nature and is usually denoted in kJ/mol (kilojoules per mole).

Bonded atoms usually go their separate ways to become individual atoms again or form different molecules. Generally, atoms form a bond due to the electrostatic attraction force existing between them. When these bonded atoms are supplied with energy, they are pulled away from each other. This pulling strength supersedes the electrostatic attraction, eventually causing the bond to break.

The bond energy incorporated indicates how strong the chemical bond is. The amount of bond energy required to break the bond increases with bond strength since more electrons are involved in the bonding, or their bond order is high. A higher bond order means a shorter bond length (distance between the bonded atoms). For instance, more bond energy is needed to break a double bond than a single bond. Triple bonds require even more energy to break than a double bond.