Explain why the electrical conductivity of a semiconductor is significantly increased if trace amounts of either donor or acceptor atoms are present, but is unchanged if both are present in equal number.

Explain whether the addition of cadmium sulfide in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of tin in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of aluminium in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of sulfur in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of gallium in trace amounts to silicon, would produce a $p$-type semiconductor.

Explain whether the addition of gallium arsenide in trace amounts to silicon, would produce a $p$-type semiconductor.

Explain whether the addition of boron in trace amounts to silicon, would produce a $p$-type semiconductor.

Explain whether the addition of lead in trace amounts to silicon, would produce a $p$-type semiconductor.

Explain whether the addition of arsenic in trace amounts to silicon, would produce a $p$-type semiconductor.

Explain whether the addition of sulfur in trace amounts to silicon, would produce a $p$-type semiconductor.

In what type of material is the energy gap between the valence band and the conduction band greatest: metal, semiconductor, or insulator? Explain.

In which of the following, $\mathrm{CO}_3^{2-}, \mathrm{SO}_2, \mathrm{CCl}_4, \mathrm{CO}$, $\mathrm{NO}_2{ }^{-}$, would you expect to find $s p^2$ hybridization of the central atom? Explain.

Describe the molecular geometry of $\mathrm{CCl}_4$ suggested by valence-bond method using hybridized atomic orbitals.