Question

How do bond energies and bond lengths of molecule help us in predicting their chemical properties? Explain with examples.

(OR) 

How can you explain with examples that bond energies and bond lengths are used to recognise chemical properties?

Answer 1

1. Bond length : 

Bond length or bond distance is the equilibrium distance between the nuclei of two atoms which form a covalent bond. 

2. Bond energy : 

Bond energy or bond dissociation energy is the energy needed to break a covalent bond between two atoms of a diatomic covalent compound in its gaseous state.

3. If the nature of the bond between the same two atoms changes the bond length also changes. For example, the bond lengths between two carbon atoms are C – C > C = C > C = C. 

4. Thus the various bond lengths between the two carbon atoms are in ethane 1.54 Å, ethylene 1.34 Å, acetylene 1.20 Å. 

5. The bond lengths between two oxygen atoms are in H₂O₂ (O-O) is 1.48 Å and in O₂(O = O) is 1.21 Å