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

Select the correct expression for determining the Packing Fraction $(P.F.)$ of an $NaCl$ unit cell (assume ideal),if ions along an edge diagonal are absent.

In a face-centered cubic $(FCC)$ unit cell,how many unit cells share an atom located at the face center?

In $NaCl$ the centres of two nearest like charged ions are present at a distance of

The number of unit cells present in $39 \ g$ of potassium if it crystallizes as a body-centered cubic $(BCC)$ structure is ($N = \text{Avogadro number}$, $\text{At. wt. of potassium} = 39$).

The ratio of the effective number of atoms in a unit cell of $fcc$ and $bcc$ lattices is