The amount of heat energy absorbed or released when one mole of a molecule is formed or dissociate due to formation of all bonds or breakage of all bonds is called “Heat Energy”.
Bond energy depends upon:
a. Polarity of molecule.
b. Bond length
a) Polarity of molecules:
Bond energy depends upon polarity of molecules; greater will be bond energy of that molecule. That is why the bond energy of polar molecules is greater as compared to non-polar molecules.
H clearly shows that due to greater electrons gravity of ‘F‘ the bond energy of HF is greater as HCL.
Bond energy also depends upon bond length of molecules. Lower the bond of a molecule greater the distance between atoms; therefore, less attraction is present between so less energy is required to decompose that molecule and vise versa, Example:
H2 ————–> 2H ∆ = 435 Kj / mole
O = O———–> 2O ∆ = 498 Kj / mole
N = N———–> 2N ∆ = 946 Kj / mole
Since the bond length of N2 molecule is smallest in the above example, therefore it has highest bond energy.