The percentage of vacant space for $bcc$ unit cell is ............. $\%$

The number of octahedral and tetrahedral holes respectively present in a hexagonal close packed $(hcp)$ crystal of $X$ atoms are

Calculate the void volume of a simple cubic unit cell if the volume of the unit cell is $5.5 \times 10^{-22} \ cm^3$.

The fraction of total volume occupied by the atoms present in a simple cubic unit cell is

Hexagonal close packed arrangement of ions is described as

In a hexagonal close-packed $(HCP)$ structure,the third layer covers the ........ holes created between the first and second layers.