1. Metals:
* Mechanism: Metals have a "sea" of free electrons that can move freely throughout the solid. These electrons carry the electrical current.
* Examples: Copper, silver, gold, aluminum, iron.
2. Some non-metals:
* Mechanism: While most non-metals are insulators, some elements like carbon in its graphite form and silicon can conduct electricity due to the presence of delocalized electrons in their structures.
* Examples:
* Graphite: The layered structure of graphite allows for the movement of electrons between the layers, making it a good conductor.
* Silicon: Silicon is a semiconductor. It has a limited number of free electrons at room temperature, but its conductivity can be significantly increased by doping with impurities. This property makes silicon essential for electronics.
3. Ionic compounds:
* Mechanism: While ionic compounds don't have free electrons, they can conduct electricity when molten (liquid) or dissolved in water. This is because the ions become mobile and can carry the current.
* Examples: Sodium chloride (NaCl), potassium bromide (KBr).
4. Semiconductors:
* Mechanism: Semiconductors have conductivity between that of conductors and insulators. Their conductivity can be controlled by temperature, doping, and other factors.
* Examples: Silicon (Si), germanium (Ge), gallium arsenide (GaAs).
Important Note: Not all solids are conductors. Insulators like rubber, glass, and plastic have tightly bound electrons that cannot move freely, preventing the flow of electricity.
