1)The conduction band is at a higher energy than the valence band. True or false?

2)No electronic states lie between the conduction and valence bands in n-type silicon. True or false?

1) True

2) False

thanks

1) The statement is true. The conduction band is at a higher energy level than the valence band in a material. To understand this, let's learn about the energy bands in solids.

In a solid material, the valence band is the energy band that is occupied by valence electrons, which are tightly bound to the atoms. The conduction band is the energy band just above the valence band and has higher energy levels. It is usually vacant or only partially occupied by electrons.

The energy gap between the valence and conduction bands is known as the band gap. This gap determines the electrical properties of the material. Conductors, such as metals, have a small or no band gap, allowing electrons to easily move from the valence band to the conduction band. Insulators have a large band gap, preventing the easy movement of electrons. Semiconductors have a small to moderate band gap, allowing some electrons to be promoted from the valence band to the conduction band under certain conditions.

2) The statement is false. In n-type silicon, there are electronic states between the conduction and valence bands. N-type silicon is a semiconductor that has been doped (contaminated) with impurities that introduce additional electrons into the crystal lattice. These impurities, typically phosphorus or arsenic, have extra valence electrons compared to the silicon atoms. These extra electrons occupy energy levels that are close to the conduction band but still within the band gap.

By introducing these extra electrons into the crystal lattice, n-type silicon increases its conductivity. These extra electrons are loosely bound and can move relatively freely, making it easier for electrical current to flow through the material. This is in contrast to intrinsic (pure) silicon, where there are no intentionally introduced impurities, and the energy levels between the conduction and valence bands are typically empty or only sparsely occupied.