The coordination number of a metal crystallizing in a hexagonal close packed structure is

In a face-centered cubic lattice of $X$ and $Y$ atoms,$X$ atoms are present at the corners while $Y$ atoms are at the face centers. If two atoms of $X$ are missing from the corners,what is the formula of the compound?

If the edge length of a cubic unit cell in an $fcc$ structure is $620 \ pm$, then the atomic radius of the element will be ............... $pm$.

$A$ compound crystallizes in a $NaCl$ type structure. What is the percentage of unoccupied tetrahedral voids?

How many particles per unit cell are present in $BCC$ structure?

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