In the sodium chloride structure, each $Na^+$ ion is surrounded by 6 $Cl^-$ ions nearest neighbours

Question

In the sodium chloride structure, each $Na^+$ ion is surrounded by 6 $Cl^-$ ions nearest neighbours and ________ $Na^+$ ion next nearest neighbours.

Professor PC Thomas Classes · Answer

In the rock salt (NaCl) structure, the $Na^+$ ions form an fcc sub-lattice. In any fcc lattice, a given atom is surrounded by 12 identical atoms as its next nearest neighbors at a distance of $a/\sqrt{2}$.