Metallic Bonds

What are Metallic Bonds?

• Metallic bonds are the forces of attraction between delocalised electrons and positive metal ions in a metal.
• Delocalised electrons are free electrons that come from the outer shells of each metal atom. These electrons can move freely and are not associated with any particular atom.
• Positive metal ions form when a metal atom loses its outer electrons and becomes positively charged.

Properties of Metallically Bonded Substances

• Metals generally have high melting and boiling points due to the strong metallic bonds that require a lot of energy to break.
• Metals are good conductors of electricity and heat because of the movement of their delocalised electrons.
• Metals are malleable (can be shaped or bent without breaking) and ductile (can be stretched into wire). These properties result from the ability of metal ions to slide over each other without breaking the metallic bonds.
• Metallic bonding leads to a regular structure which often results in metals being shiny.

Examples of Metallically Bonded Substances

• Gold (Au): Gold atoms lose electrons which become delocalised, creating a sea of free electrons. The positively charged gold ions are held in a regular lattice by their attraction to these delocalised electrons.
• Aluminium (Al): Aluminium atoms also lose electrons to form a ‘sea’ of delocalised electrons. The resultant positively charged aluminium ions are attracted to these electrons, forming metallic bonds.

Key Points of Understanding

• Understand the concept of delocalised electrons and their role in metallic bonding.
• Become familiar with the key properties of metals and be able to link these properties to the presence of metallic bonds.
• Be able to describe examples of metallic substances and explain their metallic bonding.