An oxide of $A$ crystallizes with $8$ atoms at the corners of the unit cell and $18$ oxygen atoms on the edges and on the faces symmetrically. What is the formula of this oxide?

In a $BCC$ lattice containing $X$ and $Y$ type of atoms, $X$ type of atoms are present at the corners and $Y$ type of atoms are present at the body center. In its unit cell, if three atoms are missing from the corners, the formula of the compound is:

The edge length of a face-centred cubic unit cell is $508 \ pm$. If the radius of the cation is $110 \ pm$, the radius of the anion is .............. $pm$.

If three elements $A, B, C$ crystallize in a cubic solid lattice with $B$ atoms at the cubic centers, $C$ atoms at the center of edges, and $A$ atoms at the corners, then the formula of the compound is

The number of close neighbours in a body-centred cubic $(BCC)$ lattice of identical spheres is:

If the coordination number of $Ca^{2+}$ in $CaF_2$ is $8$,then the coordination number of $F^{-}$ ion would be