How many total octahedral voids are present in a cubic unit cell?

4

The correct answer is option 2. 4

Octahedral voids (O-voids)

These voids are formed by overlapping of two trigonal voids of adjacent layers.

Surrounding spheres are located at the corners of an octahedron.

Coordination number = 6

In a unit cell of FCC type, octahedral void is located at body-center and at the edge centers of cubic unit cell.

Total number of O-voids per unit cell \(= \frac{1}{4} \times 12 + 1 \times 1 = 4\)