CBSE Class 12-science Answered

Radius ratio plays an important role in determining the structures of ionic solids and coordination number of ions. For eg.

For cations to occupy tetrahedral voids radius ratio has range = 0.225 - 0.414, coordination no. = 4.

For cations to occupy octahedral voids radius ratio has range = 0.414 - 0.732, coordination no. = 6.

If  radius ratio is more then 0.225 cation will occupy trigonal void, coordinatiion no. = 3

If radius ratio is mora than 0.732 cation will occupy cubic void, coordinatiion no. = 8.

 

Radius ratio = Radius of cation/Radius of anion.

                     = r⁺/r^-