The maximum radius of a sphere that can be fitted in the octahedral hole of a cubical closed packing of spheres of radius $r$ is $..............$ $r$.

In a cubic close-packed $(ccp)$ structure,if there are $N$ spheres,what is the number of octahedral voids?

Atoms $A$ are arranged in an $FCC$ system,and atoms $B$ occupy all the octahedral voids and half of the tetrahedral voids. The formula of the compound is:

In a crystal,atoms of $A$ form an $FCC$ lattice,atoms of $B$ occupy all octahedral voids,and atoms of $C$ occupy $25\%$ of the tetrahedral voids. The possible molecular formula of the compound is:

$A$ solid has $CCP$ arrangement having atoms $A, B, C$. If $A$ atoms are present at face centres,$B$ at corners and $C$ atoms occupy $50\%$ tetrahedral voids,then the molecular formula of the solid will be:

Calculate the packing efficiency in a simple cubic unit cell.