Question

An ionic crystal lattice has r + / r - radius ratio of 0.320, its Coordination number is options ( a ) 3 ( b ) 4 ( c ) 6 ( d ) 8

Answer 1

we know, if ionic crystal lattice has $\frac{r^+}{r^-}$ radius ratio between 0.225 to 0.414 , its coordination number is 4. because in this case ionic crystal must be tetrahedral in shape. and we know, co-ordination number of tetrahedral solid is 4. ZnS , is a good example of tetrahedral.

hence, option (b) is correct option.

Answer 2

Given:

r+ / r - = 0.320

To find:

Coordination number.

Solution:

By the property of crystal lattice structure,

r+ / r- = 0.225 to 0.414 will have a coordination number of 3.

Reason: Due to the tetrahedral shape of the crystal lattice, the coordination number will be 4.

Hence, 0.320 lies between 0.225 and 0.414.

The coordination number is 4.

The answer is ( b ) 4