Metallic bond is formed due to the attraction between kernels and the mobile electrons in a metal lattice. Metallic bond is a non-directional bond.
This bond is helpful in making the substances malleable and ductile. This is a weak bond due to the simultaneous attraction of the electrons by a large number of kernels.
There are three models which are proposed for the account of nature of bonding in metals:
1. The Free Electron Model
2. The Valence Bond Model
3. The Band Model
We will explain the Free Electron Model in detail:
The Free Electron Model:
This model is also known as the Electron Sea Model. As we know that metals can be characterized by high electrical and thermal conductivity, malleability, ductility, luster and high tensile strength.
As the valence electrons can be taken out easily in metals, metals have lower ionization energy. This means that the valence electrons are weakly bonded to the kernel. Kernel includes nucleus and electrons.
For example:
Let us take the case of lithium. The electronic configuration of Lithium is: 1s 2 2s 1
This is because lithium has only one electron in its valence shell. The positively charged kernels of metal atoms are arranged in a regular fashion in a metallic lattice. The metallic sheet maintains the flow of electrons from negative electrode to positive electrode. This constitutes electrical conductivity.
Metals have high tensile strength. Metals can resist stretching without breaking. The greater the number of valence electrons for delocalization the stronger is the metallic bond. The electrons are free and mobile in Electron Sea model. Metals have metallic bond strengths, which is intermediate to that of covalent and ionic bonds. The metals have boiling and melting point in between the ionic bond and covalent bond.
Limitations of the model:
This model does not give explanation about the vast variation in properties of the metal. For example, copper is a good conductor of electricity as compared to bismuth.
