Chapter 24, Problem 24.28QP

Interpretation Introduction

Interpretation: The difference in band gaps among conductors, semiconductors and insulators has to be explained.

Concept Introduction:

A bulk metal has number of atoms, and so have equal number of molecular orbitals.  These molecular orbitals instead of forming individual bonding orbitals and antibonding orbitals, they form a band of bonding levels and a band of antibonding levels

The gaps between the bonding band (called the valence band) and the antibonding band (called the conduction band) and the band energies helps to classify a substance as a conductor, a semiconductor, or an insulator based on the actions of the electrons in the bands

Band theory helps to study about conductors, semiconductors and insulators. The electrons of an atom will be in permitted energy levels.  These energy levels form bands. Three types of bands are available namely,

• Filled band- (found near nucleus, bears no free electrons)
• Valence band- (last band bearing valence electrons, these are free electrons)
• Conduction band – (accepts free electrons escaping from valence band)

These bands helps to explain conductivity of elements.  All the bands will lie in different energy levels.  When a free electron from valence band escapes into conduction band, conductivity takes place.  The energy gap between valence band and conduction band decides the conductivity of an element.