# Question #49b16

Jun 26, 2017

Here's my explanation.

#### Explanation:

$\text{NaCl}$ 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.

The distance from the centre of a $\text{Cl"^"-}$ ion to the centre of an $\text{Na"^"+}$ ion takes us to the centre of an edge.