The number of octabedral voids `(s)` per atoms present in a cubic packed structure is

Options

A. `1`
B. `3`
C. `2`
D. `4`

Answer

1

Explanation

In a cubic close-packed structure,if there are `n` spheres (constituent particles) in the packing ,then number of octahedral voids is also `n`.
In the cubic-close packing with fcc unit cell there are `4` spheres unit cell . Therefore there are `4` octahedral voids.
One octahedral void is present at the body centre of the cube and `12` octahedral voids are present at the centres of the `12`edges of the cube. But each void on the edge centre is shared by `4` unit cells . Hence its contribution in the unit cell `=1//4` Therefore ,the effiective number of octahedral voids in the ccp structure `=1+12xx1//4=1+3=4`
Therfore the number of octahedral voids per atom present in a cubic close packed structrue is `1`.