Question

Question #49b16

Answer 1

Here's my explanation.

Explanation:

`"NaCl"` has a cubic unit cell.

You can think of it as a face-centered cubic array of chloride ions with an interpenetrating sodium ion lattice.

(Adapted from wps.prenhall.com)

In the above diagram, there is a chloride atom at each corner and a sodium on in the centre of each edge.

The distance from the centre of a `"Cl"^"-"` ion to the centre of an `"Na"^"+"` ion takes us to the centre of an edge.

Thus, if the distance between the ions is X pm, the edge length is 2X pm.