There are three kinds of materials
- Conductors
- Insulators
- Semiconductors
Conductors
All materials having less than 4 valance electrons are called conductors. They present no resistance against electric current. e.g. Iron, Gold, Silver etc.
Insulators
All materials having more than 4 valance electrons are called Insulators. They present high resistance against electric current. e.g. Paper, Plastic, Rubber, wood etc.
Semiconductors
All materials having exact 4 valance electrons are called semiconductors. They present medium resistance against electric current. e.g. silicon, germanium etc.