Metallic bonding Revision Notes

Metals consist of atoms arranged in a regular, repeating pattern forming a giant metallic lattice. Each metal atom loses its outermost electrons to form positively charged metal ions (cations). These ions are fixed in position within the lattice.

The electrons lost by the metal atoms do not belong to any single ion but become delocalised, meaning they are free to move throughout the entire metal structure. This creates a 'sea of delocalised electrons' surrounding the metal ions.

• Metal atoms lose outer electrons to form positive ions.
• Positive metal ions form a fixed lattice structure.
• Delocalised electrons move freely throughout the lattice.

Metallic bonding is the strong electrostatic attraction between the positively charged metal ions and the negatively charged delocalised electrons. This attraction holds the metal ions together in the lattice.

Unlike ionic bonding, where electrons are transferred and fixed between ions, in metallic bonding the electrons are not associated with any particular ion but are shared collectively by all ions in the lattice.

The strength of metallic bonding depends on the number of delocalised electrons and the charge and size of the metal ions. Metals with more delocalised electrons per atom generally have stronger metallic bonds.

• Electrostatic attraction between metal ions and delocalised electrons.
• Electrons are shared collectively, not fixed between ions.
• Bond strength depends on electron number and ion charge/size.

The delocalised electrons in metals are free to move throughout the structure, allowing metals to conduct electricity. When a potential difference is applied, these electrons flow as an electric current.

This movement of electrons is possible because the electrons are not bound to any specific atom but are mobile within the metallic lattice.

This property distinguishes metals from ionic compounds, where electrons are fixed in ions and cannot move freely in the solid state.

• Delocalised electrons move freely, enabling electrical conductivity.
• Electric current is the flow of these free electrons.
• Metals conduct electricity in solid and molten states due to mobile electrons.

The strong electrostatic attraction in metallic bonding gives metals high melting and boiling points, as a large amount of energy is required to overcome the bonds.

The presence of delocalised electrons allows layers of metal ions to slide over each other without breaking the metallic bond, making metals malleable and ductile.

The metallic lattice is dense and closely packed, contributing to the typical hardness and strength of metals.

• High melting and boiling points due to strong bonding.
• Malleability and ductility from layers sliding without bond breakage.
• Dense, closely packed lattice contributes to strength.

Sodium metal consists of sodium ions (Na⁺) arranged in a lattice surrounded by delocalised electrons.

Each sodium atom loses one electron to form Na⁺ ions and one delocalised electron per atom.

The metallic bond is the attraction between Na⁺ ions and the sea of delocalised electrons, holding the structure together.

• Na → Na⁺ + e⁻ (electron becomes delocalised)
• Metallic bonding = attraction between Na⁺ ions and delocalised electrons

Metals consist of atoms arranged in a regular, closely packed lattice structure. Each metal atom loses its outermost electrons, which become delocalised and free to move throughout the entire metal lattice. The remaining metal atoms become positively charged ions (cations) fixed in position within the lattice.

This arrangement is often described as a lattice of positive metal ions surrounded by a 'sea' of delocalised electrons. The delocalised electrons are not associated with any single atom but move freely between the ions, holding the structure together by electrostatic attraction.

The metallic bond is the strong electrostatic force of attraction between the positive metal ions and the negatively charged delocalised electrons. This bonding is non-directional, meaning it acts equally in all directions around each ion.

• Metal atoms form a regular lattice of positive ions.
• Outer electrons become delocalised and free to move.
• Metallic bonding is the attraction between positive ions and delocalised electrons.
• Metallic bonds are non-directional and strong.

Electrical conductivity in metals arises because the delocalised electrons can move freely throughout the metal lattice. When a potential difference (voltage) is applied across a metal, these electrons flow as an electric current.

Unlike in ionic compounds where ions are fixed in a lattice and only conduct when molten or dissolved, metals conduct electricity in the solid state due to the mobility of their delocalised electrons.

This free movement of electrons allows metals to conduct electricity efficiently at room temperature and above.

• Delocalised electrons move freely and carry charge.
• Metals conduct electricity in solid state due to mobile electrons.
• Applying voltage causes electrons to flow as current.

Malleability is the ability of a metal to be hammered or rolled into thin sheets, while ductility is the ability to be drawn into wires. Both properties depend on the nature of metallic bonding and the structure of metals.

Because metallic bonds are non-directional, layers of metal ions can slide over each other when a force is applied without breaking the metallic bond. The delocalised electrons continue to hold the ions together even after the layers have shifted.

This sliding of layers prevents the metal from shattering and allows it to be reshaped or stretched without breaking.

• Metallic bonds are non-directional, allowing layers to slide.
• Sliding layers do not break metallic bonds.
• This enables metals to be malleable and ductile.

The lattice of positive metal ions and delocalised electrons explains key metal properties:

High electrical conductivity due to free electrons moving under an electric field.

Malleability and ductility due to non-directional metallic bonds allowing layers to slide without breaking bonds.

• Metal structure: positive ions + delocalised electrons.
• Conductivity: free electrons carry charge.
• Malleability/ductility: layers slide, bonds remain intact.