Question

KF has ccp structure. Calculate the radius of the unit cell if the edge length of the unit cell is 400 pm. How many F - ions and octahedral voids are there in the unit cell?​

Answer 1

there 16 F- ions

hope this will help you

Answer 2

GIVEN:

KF has ccp structure and edge length of the unit cell is 400pm.

To find:

Radius of unit cell, number of F⁻ ions and octahedral voids in a KF unit cell.

Solution:

Radius of a ccp unit cell in terms of edge length is given below-

r = √2×(a/4)

here r = radius of unit cell

        a = edge length of unit cell (400pm)

so putting values we get,

  r = √2 ×(400/4)

  r = √2×100

 r = 141.4pm

As KF has ccp structure which means anions occupy all corners and faces.

so total contribution is 6×(1/2) + 8×(1/8) = 4 atoms

that means 4F⁻ ions are present.

4K⁺ ions are present to balance the charge and K⁺ occupies all octahedral voids.

So, number of F⁻ ions are 4 and total octahedral voids are 4.