Metallic Bonding
Quick Notes
- Metallic bonding occurs in metals and alloys, where positively charged metal ions are attracted to a sea of negatively charged, delocalised electrons.
- Properties of metals due to metallic bonding:
- High melting and boiling points due to strong attraction between ions and electrons.
- Good conductivity because delocalised electrons can move freely and carry charge (or heat).
- Malleable and ductile as layers of ions can slide over each other without breaking the metallic structure.
Full Notes
What is Metallic Bonding?
Metallic bonding is a strong electrostatic attraction between positive metal ions (cations) and a sea of delocalised electrons. It is the bonding type that occurs in metals.
The outermost electrons of metal atoms are weakly attracted to the nucleus. As a result, these electrons can become delocalised and form a ‘sea’ of negative charge. The resulting positive metal ions are strongly attracted to this sea of delocalised electrons. This electrostatic attraction holds the structure together in a rigid, fixed arrangement.
Example:Structure of Sodium (Na)
Each sodium atom loses one outer electron, forming Na+ ions. The lost electrons become delocalised, forming an electron cloud.
There is strong attraction between Na+ ions and the delocalised electrons, which holds the metal together.
Properties of Metals Explained by Metallic Bonding
1. High Melting and Boiling Points
Strong electrostatic forces between positively charged ions and delocalised electrons require a large amount of energy to overcome and break.
2. Electrical and Thermal Conductivity
Delocalised electrons are free to move, allowing them to carry charge or heat energy.
Metals conduct electricity in both solid and molten states.
Example: Copper (Cu) is used in electrical wiring due to its high conductivity.
3. Malleability and Ductility
Metal ions are arranged in layers that can slide over each other without breaking the attraction between ions and delocalised electrons.
Malleability means can be hammered into shapes.
Ductility means can be drawn into wires.
Example:Gold (Au) is highly malleable and used for jewellery.
Comparison of Metallic, Ionic, and Covalent Bonding
| Property | Metallic Bonding | Ionic Bonding | Covalent Bonding |
|---|---|---|---|
| Structure | Positive ions in a sea of electrons | Lattice of positive and negative ions | Shared pairs of electrons |
| Melting/Boiling Point | High | High | Low (except giant covalent) |
| Conductivity | Conducts as a solid and liquid | Conducts when molten or in solution | Does not conduct (except graphite) |
| Malleability | High | Brittle | Varies |
Summary
- Metallic bonding is the electrostatic attraction between positively charged ions and delocalised electrons.
- This bonding explains metals’ high melting points, electrical conductivity, and malleability.
- Metals are strong yet malleable due to the ability of layers of ions to slide while maintaining metallic bonds.
- Comparison:
- Metallic bonding → positive ions in a sea of electrons.
- Ionic bonding → lattice of positive and negative ions.
- Covalent bonding → shared pairs of electrons.