Question

1. Classify each of the following solids as ionic, metallic, molecular, network or amorphous.

• I₂
• Plastic
• LiBr
• SiC

 2. In terms of band theory differentiate Conductors, insulators & semi conductors.

Answer 1

1. Classification of solids as ionic, metallic, molecular, network or amorphous.

• I₂ – Molecular 
• Plastic – Amorphous 
• LiBr – Ionic 
• SiC – Covalent

 2. Differences between Conductors, insulators & semi conductors.

• Conductors : The valence band overlaps with the conduction band or no energy gap exists between them.
• Insulators : The energy gap between valance band and conduction band is very large. Hence electrons from valence band cannot move into the conduction band. Semi conductors have small energy gap between valence band and conduction band.