(h) Metallic bonding
- Syllabus
- 2024
- Topic
- —
- Level
- —
Learning objectives
Represent a metallic lattice in two dimensions
A 2-D metallic-lattice diagram represents a regular array of positive metal ions surrounded by delocalised electrons.
| Diagram feature | Meaning |
|---|---|
| equal circles arranged in repeating rows | positive metal ions in fixed lattice positions |
| + inside each large circle | positive charge of each metal ion |
| many small dots or crosses between the ions | delocalised electrons spread through the structure |
Repeat the pattern beyond one pair of ions so the diagram clearly shows a lattice rather than a molecule. Place the electron symbols in the spaces throughout the array, not attached to one particular ion.
This is a schematic 2-D model of a three-dimensional solid. Circle size, spacing and electron positions are not to scale; the meaningful features are the repeating positive ions and electrons that are not localized to one atom.
Define metallic bonding electrostatically
Metallic bonding is the strong electrostatic attraction between a lattice of positively charged metal ions and delocalised electrons.
Outer electrons are no longer associated with one metal atom; they move throughout the structure. Their negative charge attracts the positive ions in every direction and holds the giant metallic lattice together.
| Component | Charge and arrangement |
|---|---|
| metal ions | positive; arranged in a regular lattice |
| delocalised electrons | negative; spread and mobile throughout the lattice |
Metallic bonding is not attraction between neutral atoms, between opposite ions, or between a shared pair and two nuclei. The required attraction is specifically between positive metal ions and delocalised electrons.
Explain conductivity and malleability of metals
The metallic lattice contains mobile delocalised electrons and non-directional attraction between ions and electrons. These structural features explain electrical conductivity and malleability.
| Property | Structural cause | Explanation |
|---|---|---|
| electrical conductivity | delocalised electrons are free to move | electrons flow through the lattice and carry charge |
| malleability | layers of positive ions can slide past one another | attraction to the delocalised electrons remains, so the metal changes shape without the lattice immediately splitting |
The charge carriers are electrons, not moving metal ions. When a force shifts one layer, the electron attraction is not tied to fixed pairs of atoms, so bonding can continue across the rearranged layers.
Do not describe metals as layers of molecules or claim that conductivity comes from positive ions flowing through a solid. Malleability means a metal can be hammered or pressed into shape; it is not the same as softness.