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?

The coordination number of an atom in a body-centered cubic $(BCC)$ structure is:
[Assume that the lattice is made up of atoms.]

In a cubic crystal structure,'$W$' atoms are at the corners of the cube,'$O$' atoms are at the edges,and '$Na$' atoms are at the body center. Determine the formula of this crystal.

The tetrahedral voids formed by $ccp$ arrangement of $Cl^{-}$ ions in rock salt structure are

If $Z$ is the number of atoms in the unit cell that represents the closest packing sequence $ABCABC$,the number of tetrahedral voids in the unit cell is equal to

$A$ cubic structure is formed where atoms of element $X$ are occupied at the corners of the cube and also at the face centers. Atoms of element $Y$ are present at the body center and at the edge centers. If all the atoms are removed along a plane passing through the middle of the cube (bisecting the four edges),the formula will become