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

How many "nearest" and "next nearest" neighbours,respectively,does potassium have in a $bcc$ lattice?

In a compound formed by $A^{+}$ and $B^{-}$ ions,$B^{-}$ ions are arranged at all corners except two and at all face centers except three,while $A^{+}$ ions are at the midpoints of all body diagonals. The molecular formula of the compound will be ................

The coordination number of the sphere in cubic close packed $(ccp)$ structure is

The number of nearest neighbours and next nearest neighbours of an $Na^{+}$ ion in a crystal of $NaCl$ are respectively

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