The Solid State

For tetrahedrtal coordination Radius ratio is 0.225-0.414.

CsCl has a body centred cubic structure.

In case of semiconductors, the gap between the valence band and conduction band is small  Therefore, some electrons may jump to conduction band and show some conductivity. Electrical conductivity of semiconductors increases with rise in temperature, since more electrons can jump to the conduction band.

It is the ratio of the radius of the cation to the radius of the anion in an ionic crystal.the radius ratio of tetahedral is in between 0.225-0.732. Its ideal value is 0.225 for tetrahedral void.