What are delocalised electrons in relation to metallic bonding?

Delocalised electrons in metallic bonding are the free-moving electrons shared among a network of positively charged ions.

In more detail, metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons, which are often referred to as delocalised electrons, and positively charged metal ions. This type of bonding is unique to metals and it gives rise to many of the characteristic properties of metals such as their high electrical conductivity, malleability, and ductility.

The term 'delocalised' refers to the fact that these electrons are not associated with a single atom or a covalent bond. Instead, they are free to move throughout the entire structure of the metal. This is often described as a 'sea of electrons' that surrounds the metal ions. The delocalised electrons are shared among a network of metal ions, forming what is often referred to as an 'electron cloud'. This cloud is highly mobile and is responsible for the high electrical and thermal conductivity of metals.

The delocalised electrons also contribute to the malleability and ductility of metals. Because the electrons are not tied to specific atoms, they can move and adjust to changes in the arrangement of the metal ions. This allows the metal to be deformed without breaking, which is why metals can be hammered into sheets (malleability) or drawn into wires (ductility).

In terms of energy levels, these delocalised electrons occupy what is known as a 'band' of energy levels. This band is partially filled with electrons, which allows them to move to higher energy levels when energy is applied, such as in the form of heat or electricity. This movement of electrons is what allows metals to conduct electricity and heat.

In summary, delocalised electrons play a crucial role in metallic bonding and are responsible for many of the characteristic properties of metals. They are free-moving, shared among a network of metal ions, and contribute to the high electrical and thermal conductivity, malleability, and ductility of metals.