Question

Percentage of free space in a body centred cubic unit cell is:

• A. $30\text{\%}$
• B. $34\text{\%}$
• C. $28\text{\%}$
• D. $32\text{\%}$

Answer 1

The correct option is D $32\text{\%}$

The ratio of volumes occupied by atoms in unit cell to the total volume of the unit cell is called as packing fraction or density of packing. For body centred cubic structure, packing fraction $=0.68i.e.,68\text{\%}$ of the unit cell is occupied by atoms and $32\text{\%}$ is empty.