The correct coordination number for the zinc ion in the zinc blende crystal structure is:

$CsCl$ crystallises in a body-centred cubic $(BCC)$ lattice. If '$a$' is its edge length,then which of the following expressions is correct?

The arrangement of $X^{-}$ ions around $A^{+}$ ion in solid $AX$ is given in the figure. If the radius of $X^{-}$ is $250 \ pm$, the radius of $A^{+}$ is: (in $pm$)

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

Calculate the total volume occupied by all atoms in a simple cubic unit cell if the radius of the atom is $3 \times 10^{-8} \ cm$.

The edge lengths of a simple cubic $(sc)$ and a face-centered cubic $(fcc)$ unit cell are equal. The ratio of the volume occupied by atoms in these two structures is .....