Show that in a cubic close packed structure, eight tetrahedral voids are present per unit cell.

 

 
Cubic close packed structure contains one atom at each corner of an unit cell and at face centre of each unit cell. Each unit cell consists of 8 small cubes.

Each small cube contains 4 atoms at its alternate corner when these atoms are joined to each other lead to creation of a tetrahedral void as shown below

Since, there are total 8 smaller cubes present at one unit cell and each smaller cube has one tetrahedral void hence, total numberof tetrahedral void present in each unit cell is equal to eight. 

As we know ccp structure has 4 atoms per unit cell. Thus, total number of tetrahedral void in one ccp unit cell is equal to 8.