# The Solid State

Question 61

## For tetrahedral co-ordination, what should be the range of radius ratio (r+/r–) value?

Solution
For tetrahedrtal coordination Radius ratio is 0.225-0.414.
Question 62

## What type of structure possessed by a unit cell of CsCl.

Solution
CsCl has a body centred cubic structure.
Question 63

## What is the effect of increasing temperature on the conductivity of semi-conductors?

Solution
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.
Question 64

## Define radius ratio. What is the ideal value for a tetrahedral void?

Solution
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.