What is the coordination number of $Zn$ in the crystal structure of $Zn$?

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:

In a hexagonal close packing $(hcp)$ lattice,each sphere touches ................... spheres in its own layer.

Which of the following structures is not correctly matched?

$A$ compound made of elements $A$ and $B$ forms an $fcc$ structure. Atoms of $A$ are at the corners and atoms of $B$ are present at the centres of the faces of the cube. What is the formula of the compound?

Potassium fluoride $(KF)$ has an $NaCl$ type structure. What is the distance between $K^{+}$ and $F^{-}$ ions if the unit cell edge length is $a \ cm$?