You can easily bend a copper wire, but try bending a solid crystal of salt and it will snap. This is because metals have a unique internal structure that allows their internal particles to shift without breaking the solid apart.
Metals exist as a giant metallic lattice. This is a large-scale, regular, repeating three-dimensional arrangement of particles. The formation of this structure happens in a specific way:
The metallic bond is defined as the strong electrostatic attraction between the positive metal ions and the surrounding sea of negatively charged delocalised electrons.
Because this electrostatic attraction is very strong, it acts in all directions and holds the lattice firmly together. This means large amounts of energy are required to overcome these bonds, which explains why most metals have very high melting and boiling points (for example, iron melts at ).
The strength of a metallic bond depends on two main factors: the magnitude of the positive charge on the metal ion, and the number of delocalised electrons contributed by each atom.
Compare the melting points of Sodium and Magnesium to determine which has the stronger metallic bonding.
Step 1: Identify the groups and the ions formed.
Step 2: Compare the charges and electron quantities.
Step 3: Conclude on the bond strength.
Metals are excellent electrical and thermal conductors in both their solid and liquid states. The delocalised electrons act as mobile charge carriers that are free to move and transfer electrical charge or heat energy rapidly through the entire lattice.
Pure metals are also malleable (can be hammered into shape) and ductile (can be drawn into wires). Inside the lattice, the positive metal ions are arranged in regular layers. When a force is applied, these layers can slide over each other. The metallic bonds do not break when the layers shift because the delocalised electrons simply move to maintain the electrostatic attractions.
Metallic, ionic, and covalent bonds are all primary bonds held together by electrostatic attraction. However, the exact particles involved and the nature of the attraction differ significantly.
| Feature | Metallic | Ionic | Covalent |
|---|---|---|---|
| Particles involved | Positive metal ions and delocalised electrons | Oppositely charged ions (cations and anions) | Atoms (sharing electrons) |
| Nature of Bond | Electrostatic attraction between positive ions and negative electrons | Electrostatic attraction between oppositely charged ions | Electrostatic attraction between shared pairs of electrons and positive nuclei |
| Typical Arrangement | Giant metallic lattice | Giant ionic lattice | Simple molecules or giant covalent structures |
| Conductivity | Conducts in solid and liquid states (due to delocalised electrons) | Conducts only when molten or in aqueous solution (due to mobile ions) | Generally non-conductors (except graphite/graphene) |
Students often describe the metallic lattice as being made of 'atoms' surrounded by electrons. OCR mark schemes strictly require you to say 'positive metal ions' or 'cations'.
Never use the term 'intermolecular forces' when discussing metallic bonding. Intermolecular forces only exist between simple covalent molecules, not in giant metallic lattices.
When drawing a diagram of a metallic lattice, ensure you draw the positive ions in a regular grid with at least two rows to correctly show a 'lattice', and scatter small dots randomly between them to represent the delocalised electrons.
In 'Compare' questions about conductivity, you must specify what is moving: state that 'delocalised electrons' carry charge in solid metals, whereas 'mobile ions' carry charge in molten ionic compounds.
Giant metallic lattice
A regular, repeating three-dimensional arrangement of positive metal ions surrounded by a sea of delocalised electrons.
Delocalised electrons
Electrons that are not bound to a specific atom and are free to move throughout a giant lattice.
Positive metal ions
Atoms that have lost their outer shell electrons to achieve stability, gaining a positive overall electrical charge.
Cations
A positively charged ion, formed when an atom loses electrons.
Anions
A negatively charged ion, formed when an atom gains electrons.
Metallic bond
The strong electrostatic attraction between positive metal ions and a sea of delocalised electrons.
Electrostatic attraction
The pulling force between particles with opposite electrical charges.
Mobile charge carriers
Charged particles, such as delocalised electrons or mobile ions, that are free to move through a structure and conduct electricity.
Malleable
The ability of a substance to be hammered or pressed into a new shape without breaking or cracking.
Ductile
The ability of a material to be stretched into a wire without breaking.
Giant structure
A large-scale arrangement of atoms, ions, or molecules where the pattern repeats throughout the entire substance.
Valence electrons
The electrons found in the outermost shell of an atom that can participate in the formation of chemical bonds.
Put your knowledge into practice — try past paper questions for Chemistry A
Giant metallic lattice
A regular, repeating three-dimensional arrangement of positive metal ions surrounded by a sea of delocalised electrons.
Delocalised electrons
Electrons that are not bound to a specific atom and are free to move throughout a giant lattice.
Positive metal ions
Atoms that have lost their outer shell electrons to achieve stability, gaining a positive overall electrical charge.
Cations
A positively charged ion, formed when an atom loses electrons.
Anions
A negatively charged ion, formed when an atom gains electrons.
Metallic bond
The strong electrostatic attraction between positive metal ions and a sea of delocalised electrons.
Electrostatic attraction
The pulling force between particles with opposite electrical charges.
Mobile charge carriers
Charged particles, such as delocalised electrons or mobile ions, that are free to move through a structure and conduct electricity.
Malleable
The ability of a substance to be hammered or pressed into a new shape without breaking or cracking.
Ductile
The ability of a material to be stretched into a wire without breaking.
Giant structure
A large-scale arrangement of atoms, ions, or molecules where the pattern repeats throughout the entire substance.
Valence electrons
The electrons found in the outermost shell of an atom that can participate in the formation of chemical bonds.