In a face-centred cubic $(FCC)$ unit cell,what fraction of the edge length is not covered by the constituent atoms?

What is the mass of an $fcc$ unit cell if the mass of one atom of an element is $6 \times 10^{-23} \ g$?

The coordination number in $hcp$ is

The number of unit cells present in $39 \ g$ of potassium if it crystallizes as a body-centered cubic $(BCC)$ structure is ($N = \text{Avogadro number}$, $\text{At. wt. of potassium} = 39$).

In a solid $AB$,$A$ atoms are in $ccp$ arrangement and $B$ atoms occupy all the octahedral sites. If two atoms from the opposite faces are removed,then the resultant stoichiometry of the compound is $A_{x} B_{y}$. The value of $x$ is ..... [nearest integer]

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