Semiconductors- 1

Question 1

what is valence band

Answer 1

It is the lower band of energy which contains the energy levels of valence electrons.

This band is never empty

They electrons in this band do not contribute to electric current.

Question 2

what is conduction band

Answer 2

It is an upper band of energy in which the electrons are not present at 0K.

Electrons gain energy and go to this level.

The electrons in this level contribtue to electric current.

Question 3

metallic conductors energy band gap

Answer 3

With no external energy, all
the valence electrons will reside in the valence band. If the lowest level in
the conduction band happens to be lower than the highest level of the
valence band, the electrons from the valence band can easily move into
the conduction band. Normally the conduction band is empty. But when
it overlaps on the valence band electrons can move freely into it. This is
the case with metallic conductors.

Question 4

insulators

Answer 4

If there is some gap between the conduction band and the valence
band, electrons in the valence band all remain bound and no free electrons
are available in the conduction band. This makes the material an
insulator.

Question 5

what is energy gap/ energy band gap

Answer 5

It is the separation between the highest energy level of the valence band and the lowest energy level of the conduction band.

The minimum amt of energy required for shifting electrons from valence band to conduction band is called energy band gap.

Question 6

classification of elements: metals