Factors Influencing Bond Energy

Chemical Bonding

This entry defines the term ‘bond energy’ and gives a brief but comprehensive description of its influencing factors. 

What is bond energy? 

The term ‘bond energy’ refers to the power required to break a bond between two atoms in a diatomic molecule. In other words, it is the energy released in the formation of a chemical bond from free atoms.


Let us take an example of a hydrogen molecule to explain the release and absorption of heat during the formation and dissociation of a diatomic molecule.  

Bond Energy: Formation and dissociation of Hydrogen molecule
Bond Energy: Formation and dissociation of a Hydrogen molecule

In the equation given above, we can see that two molecules combine together to form a molecule ‘H2’ whereas the ‘Heat’ signifies the energy released. The heat released during the formation of a hydrogen molecule is 436Kj/Mol. 

It would need the same amount of energy (436KJ/Mol) to break the molecule into its component atoms. 

Thus, energy is always released in bond formation and absorbed in bond dissociation as illustrated in the equation above. 

How do chemists measure the energy required to break a diatomic bond?

Chemists measure required power for dissociation of a bond in ‘Kilojoule/mole (Kj/mole)’. It can be maybe of two types i.e. ‘exothermic’ and ‘endothermic’ depending upon the formation and breakdown of a bond respectively. 

For instance, in the example given above, the heat was released during the formation of a bond a diatomic molecule of hydrogen gas. The energy was released as a result of the formation. This is an example of Exothermic energy. 

What are the factors that influence ‘bond energy’? 

The following are the factors influencing the energy released and required during the formation and dissociation of a molecule:  

1. Polarity of Molecules

The term ‘polarity of molecules’ means is the distribution of electrical charge over atoms bonded together in a molecule.  

Molecules with the ionic character always have shortened bond length. It is because the cohesive forces between the atoms are stronger. Hence, more energy would be needed to dissociate a diatomic molecule.  

2. Bond length

The term ‘bond length’ refers to the distance between nuclei in a molecule of two atoms. The shorter the bond length, the stronger and firmer the bonds.

Similarly, the longer the bond length, the weaker the nuclear bonds. Thus, more energy would be needed to break a molecule with a shorter bond length.  Also Check Thailand government Scholarship

3. Bond Order

The term ‘bond order’ refers to the number of chemical bonds between atoms in a diatomic molecule.

The Bond order indicates the stability of the bond. The more chemical bond, the more stable is the molecule. In other words, the more chemical bonds, the more energy is needed to break a molecule. Bond energy is high with an increased bond order. 

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