Coordination numbers of $Zn^{2+}$ and $S^{2-}$ in the crystal structure of wurtzite are

The radius of the largest sphere which fits properly at the centre of the edge of a body-centered cubic $(BCC)$ unit cell is (Edge length is represented by $a$) (in $a$)

Select the correct expression for determining the Packing Fraction $(P.F.)$ of an $NaCl$ unit cell (assume ideal),if ions along an edge diagonal are absent.

$A$ 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:

How is the anti-fluorite structure derived from the fluorite structure?

An $fcc$ unit cell of aluminium contains the equivalent of how many atoms?