In a face-centred cubic $(FCC)$ unit cell,what is the contribution of an atom located at the face to the unit cell?

The radius of $Na^{+}$ is $95 \, pm$ and the radius of $Cl^{-}$ ion is $181 \, pm$. What is the coordination number of $Na^{+}$?

$A$ metal $X$ crystallises in a face-centred cubic arrangement with the edge length $862 \, pm$. What is the shortest separation of any two nuclei of the atom? ........... $\, pm$

In the rock salt structure,the number of formula units per unit cell is equal to

Coordination number of $Na^{+}$ ion in rock salt is

What is the coordination number of the $hcp$ crystal lattice?