The coordination number of an atom in a hexagonal close-packed $(hcp)$ structure is ...........

What is the minimum value of the radius ratio ${r_ + }/{r_ - }$ for $NaCl$ to ensure that anion-anion contact does not occur?

What is the coordination number of a particle in an $fcc$ crystal lattice?

The compound $AB$ crystallizes in a cubic lattice in which both $A$ and $B$ atoms have coordination numbers of $8$. To what crystal class does the unit cell belong?

The coordination number of an atom in a body-centered cubic $(BCC)$ structure is:
[Assume that the lattice is made up of atoms.]

In solid $CsCl$,each $Cl^{-}$ ion is closely packed with how many $Cs^{+}$ ions?