Bond energy and Bond length and Metallic bond

BOND ENERGY

Definition:
·      The energy required to break a bond between the two bonded atoms is called bond energy.
Or

·      The energy required to convert one mole of a diatomic molecular substance in the gaseous state into its free atoms is known as bond energy. 

·      As the bond energy increases, the stability of the bond also increases.
·      sigma - bonds are stronger than pi bonds
·      Number of bonds between atoms increases the overall bond strength increases
-C-C- < -C=C- < -CC-

BOND LENGTH AND ENGERY



BOND LENGTH

Definition: The distance between the centres of the nuclei of two covalently bonded atoms is known as bond length.
·      Bond lengths are measured in angstroms or nanometers.



 METALLIC BOND

·      Properties of Metals:
1.      Metals are good electrical and thermal conductors
2.      They are opaque and have high refracting power
3.      They have high melting and boiling points
4.      They crystallise with high coordination numbers of 12 or 14
5.      The above properties of metals cannot be explained on the basis of normal ionic or covalent Bond. 

ELECTRON SEA MODEL
·      Each atom in a metal crystal loses all its valence electrons.
·      Valence electrons are free to move throughout the metal crystal lattice.
·      These delocalized electrons are common property of all the ions present in the metal lattice.
·      A force of attraction develops between negative charged electron and positive metal ion.


Definition: The force that binds a metal ion to the mobile electrons within its sphere of influence is known as metallic bond


 Metallic Properties

Electron –Sea model very well explains the
following metallic properties
1) Metallic lustre
2) Electrical conductivity
3) Thermal conductivity
4) Malleability and Ductility



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