What is the coordination number of each sphere in a two-dimensional hexagonal close-packed structure?

The structure of $ZnS$ is

$A$ solid has a structure in which $W$ atoms are located at the corners of a cubic lattice,$O$ atoms are at the center of the edges,and $Na$ atoms are at the center of the cube. The formula for the compound is:

Calculate the volume of a unit cell having an atomic radius of $141.4 \ pm$ forming an $fcc$ unit cell.

If a metal has a $fcc$ crystal structure,the coordination number is $12$ because

What is the percentage of void space in $bcc$ type of unit cell (in $\%$)?