Explain about metallic bonding.

Explanation

(i) The forces that keep the atoms of the metal so closely in a metallic crystal constitute what is known as metallic bond.
(ii) According to Drude and Lorentz, metallic crystal is an assemblage of positive ions immersed in a gas of free electrons. The free electrons are due to ionisation of the valence electrons of the atoms of the metal.
(iii) As the valence electrons of the atoms are freely shared by all the ions in the crystal, the metallic bonding is referred to as electronic bonding.
(iv) The electrostatic attraction between the metal ions and the free electrons yield a three dimensional close packed crystal with a large number of nearest metal ions. So metals have high density.
(v) As the close packed structure contains many slip planes along which movement can occur during mechanical loading, metal acquires ductility.
(vi) As metal ion is surrounded by electron cloud in all directions, the metallic bonding has no directional properties.
(vii) As the electrons are free to more around the positive ions, the metals exhibit highelectrical and thermal conductivity.
(viii) The metallic lustre is due to the reflection of light by the electron cloud.
(ix) As the metallic bond is strong enough, the metal atoms are reluctant to break apart into a liquid or gas, so the metals have high melting and boiling points.
(x)High thermal conductivity of metals is due to thermal excitation of many electons from the valence bond to the conduction band.