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

In detail, metallic bonding is a specific type of chemical bonding that emerges from the electrostatic attraction between conduction electrons—commonly known as delocalised electrons—and positively charged metal ions. This bonding mechanism is characteristic of metals and is responsible for many of their notable properties, including high electrical conductivity, malleability, and ductility.

The term “delocalised” signifies that these electrons are not confined to a single atom or covalent bond. Rather, they are free to move throughout the entire metallic structure. This phenomenon is often described as a “sea of electrons” that envelops the metal ions. The delocalised electrons are shared among a network of metal ions, creating what is frequently referred to as an “electron cloud.” This cloud is highly mobile, contributing significantly to the excellent electrical and thermal conductivity of metals.

Moreover, delocalised electrons enhance the malleability and ductility of metals. Since these electrons are not bonded to specific atoms, they can adjust and relocate in response to changes in the arrangement of the metal ions. This property allows metals to be deformed without fracturing, which is why they can be hammered into sheets (malleability) or drawn into wires (ductility).

From an energy perspective, delocalised electrons occupy what is known as a “band” of energy levels. This band is only partially filled with electrons, enabling them to transition to higher energy levels when energy is supplied, such as through heat or electricity. This movement of electrons facilitates the conduction of both electricity and heat in metals.

In summary, delocalised electrons are integral to metallic bonding and are fundamental to many of the distinctive properties of metals. They are free-moving, shared among a network of metal ions, and are key contributors to the high electrical and thermal conductivity, malleability, and ductility observed in metallic materials.