4.4 - Metallic bonding
4.4.1: Describe the metallic bond as the electrostatic atraction between a lattice of positive ions and delocalised electrons.
Atoms cannot exist on their own as they are too unstable under normal conditions (except the noble gases).
Metal atoms have outer shells in which the electrons can be easily lost. They are said to be easily ionised.
However, in the absence of anything to give the electrons to, the metal atoms agglomerate and share the electrons between them. This gives rise to a giant lattice of ions held together by delocalised electrons. This is metallic bonding.
The delocalised electrons are electrostatically attacted to the positive ions and hold the whole structure together. This force of attraction is dependent on the magnitude of the positive charged ions and the number of electrons in the delocalised orbital. It is then attenuated by the size of the ions themselves; larger ions = weaker force.
4.4.2: Explain the electrical conductivity and malleability of metals. AIM 8: Students should appreciate the economic importance of these properties and the impact that the large scale production of iron and other metals has made on the world.
The delocalised electrons are free to move throughout the metal structure. If a potential difference is applied across the metal, electrons can flow into the metal and out the other side. The metal is a conductor.
The forces of electrostatic attraction within the metal lattice are non-directional. Distortion of the lattice does not affect the force of attraction to any great extent and so the metal can be bent into shape without breaking. This is called malleability.