What is the total number of tetrahedral voids in $0.6 \ mole$ of a compound that forms a $hcp$ structure?

Calculate the packing efficiency in a simple cubic unit cell.

$A$ two-dimensional solid pattern formed by two different atoms $X$ and $Y$ is shown below. The black and white squares represent atoms $X$ and $Y,$ respectively. The simplest formula for the compound based on the unit cell from the pattern is

The anions $(A)$ of a $C_{p}A_{q}$ molecule form an $fcc$ lattice. Cations $(C)$ are positioned at the body center and half of the edge centers. The formula of the molecule is:

$A$ crystalline solid $XY_3$ has a $ccp$ arrangement for its element $Y$. $X$ occupies:

$A$ metal crystallises in a face-centred cubic $(fcc)$ structure. If the edge length of its unit cell is $a$,the closest approach between two atoms in the metallic crystal will be: