In a closed packed array of $N$ spheres,the number of tetrahedral holes is

What is the percentage of unoccupied space in $fcc$ unit cell (in $\%$)?

In a compound made of atoms $A$ and $B$,atoms $A$ form an $fcc$ lattice,while atoms $B$ occupy $25\%$ of the tetrahedral voids and $50\%$ of the octahedral voids. If the crystal is cut such that all face-centered atoms along one axis are removed,the molecular formula of the resulting solid will be ...........

The close packing that represents the $ABC ABC......$ order is:

Explain the formation of voids during the transition from a two-dimensional hexagonal close-packed layer to a three-dimensional close-packed structure.

How will you distinguish between the following pairs of terms:
$(iii)$ Tetrahedral void and octahedral void?