Metallic Bonding

The Structures of Metals

Metals, like ionic substances, exist in a lattice when solid and, like ionic solids and giant covalent structures, contain millions of atoms. However, unlike the lattice of an ionic solid, metal lattices do not alternate between positive and negative ions. Instead, metals exist as a lattice of positive metal ions, surrounded by a “sea” of delocalised electrons.  This sea of electrons is created when metal atoms come together and all give up their outer shell electrons to form a shared group between them. The now positively charged metal ions are attracted to the sea of electrons through strong electrostatic forces. This resulting attraction is what we call metallic bonding. 

Properties of Metals

The properties of metals are a result of the forces of electrostatic attraction between the positive metal lattice, and negative “sea” of delocalised electrons. This electrostatic attraction is very strong, and requires a lot of energy to over come. As a result, metals typically have high melting points (often ranging from 400\degree \text{C} to over 3000\degree \text{C}) There are some exceptions to this trend however. Mercury has the lowest melting point of all the metals, all the way down at \text{-}39\degree \text{C}. 

Metals are also able to conduct electricity when solid. This is because the delocalised electrons in the metal structure are not fixed in place and can move around freely. This lets them carry an electric charge, even when the metal is in the solid state (unlike ionic compounds which can only conduct when molten or in solution). Electrons can also carry thermal energy through the solid, making metals good conductors of heat as well as electricity. 

The lattice structure of metals means that they are also very ductile (they can be bent and formed into different shapes). Because the metal ions arranged in layers, they are able to slide over one another if a force is applied. This sliding will change the overall shape of the metal, allowing it to be shaped.

Unlike ionic solids, metals are not typically soluble in water. This is because the attraction between the positive metal lattice and negative “sea” of electrons is much stronger than that between the ions and water.