What is the coordination number in a calcium fluoride $(CaF_2)$ type structure?

The coordination number of $Na^{+}$ in $NaCl$ is

In a face-centred cubic $(FCC)$ unit cell,what fraction of the edge length is not covered by the constituent atoms?

$A$ crystal is formed by two elements $X$ and $Y$ in a cubic structure. $X$ atoms are at the corners of a cube,while $Y$ atoms are at the face centers. The formula of the compound will be:

The number of octahedral voids in a unit cell of a cubical closest packed structure is

In the closest packed structure of a metallic lattice,the number of nearest neighbours of a metallic atom is