1. Electron Mobility:
* Metals: Metals have a "sea" of free electrons. These electrons are loosely bound to their atoms and can easily move throughout the material. When a voltage is applied, these free electrons flow, creating an electric current.
* Plastics: Plastics are typically made up of long chains of molecules held together by strong covalent bonds. These bonds tightly hold electrons to the atoms, making them very difficult to move. There are very few free electrons available to carry an electrical current.
2. Band Structure:
* Metals: Metals have overlapping energy bands, allowing electrons to easily move to higher energy levels and contribute to conduction.
* Plastics: Plastics have a large energy gap between their valence band (where electrons are normally found) and conduction band (where electrons can move freely). This gap requires a significant amount of energy to excite electrons into the conduction band, making them poor conductors.
3. Insulating Properties:
* Metals: Due to their high conductivity, metals are generally considered good conductors and are often used in electrical wiring and components.
* Plastics: Their lack of free electrons and large band gap makes them excellent insulators. This property is why plastics are widely used in electrical insulation, covering wires, and creating protective casings for electronic devices.
In summary:
The difference in electrical conductivity between metals and plastics boils down to the availability of free electrons. Metals have a large supply of these electrons, allowing for easy current flow. Plastics, with their tightly bound electrons and large energy gaps, restrict the movement of electrons, making them poor conductors and effective insulators.
