Sodium chloride, NaCl, usually crystallises in a face
centred cubic lattice. How many ions are in contact
with any single Na+ ion ?
Answers
Answer:
6 ions
Explanation:
In solid sodium chloride, each ion is surrounded by 6 ions of the opposite charge as expected on electrostatic grounds. The surrounding ions are located at the vertices of a regular tetrahedron. In the language of close packing, the larger chloride ions are arranged in a cubic array whereas the smaller sodium ions fill all the cubic gaps (tetrahedral voids) between them. This same basic structure is found in many other compounds and is commonly known as the halite or rock salt crystal structure. It can be represented as face centered cubic (FCC) lattice with a two atom basis or as two interpenetrating face centered cubic lattice. The first atom is located at each lattice point, and the second atom is located halfway between lattice points along the FCC uni cell edge.