Single Bond Energies Table

Knowing the values for bond energy helps us to predict whether a reaction will be exothermic or endothermic. For example, if the bonds in the product molecules are stronger than the bonds of the reactant molecules, then the products are more stable and have a lower energy than the reactants, and the reaction is exothermic. If the reverse is true, then energy (heat) must be absorbed in order for the reaction to occur, making the reaction endothermic. In this case, the products have a higher energy than the reactants. Bond energies may be used to calculate change in enthalpy, ΔH, for a reaction by applying Hess's Law. ΔH can be obtained from the bond energies only when all of the reactants and products are gases.

Single Bond Energies (kJ/mol) at 25°C
	H	C	N	O	S	F	Cl	Br	I
H	436	414	389	464	339	565	431	368	297
C		347	293	351	259	485	331	276	238
N			159	222	—	272	201	243	—
O				138	—	184	205	201	201
S					226	285	255	213	—
F						153	255	255	—
Cl							243	218	209
Br								193	180
I									151