The number of octahedral sites per sphere in a $fcc$ structure is

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 cubic structure of a compound made from $X$ and $Y$,where $X$ atoms are at the corners of the cube and $Y$ atoms are at the face centers of the cube,the molecular formula of the compound is:

The crystal structure of $NaCl$ is:

In $NaCl$ type structure, the shortest distance between two nearest neighbours is $100 \ pm$. Then, the distance between two next nearest neighbours in the same unit cell will be:

The coordination number of a sphere in a face-centered cubic $(fcc)$ lattice is .....